Flightgame

Play online: https://noname-ch.github.io/flightgame/ (updates automatically with every push to main)

What we could build next: see ROADMAP.md.

A small airline management game in the browser, in a dark theme. The start screen lets you continue your saved airline or found a new one: pick its name, the mode, the difficulty, your home airport (30 small airports across the world with cheap slots, startAirports in config.js) and your first leased aircraft (ATR 72, Dash 8-400, E190, A220-300, A320neo or 737-800). The default is Bern-Belp (BRN) with an Airbus A220-300.

Quick start (top of the start screen) skips the setup for testing: one click starts a ready-made airline whose planes already fly daily timetables (Swiss regional, European network, Widebodies, Busy hub with 20 planes, Sandbox with CHF 1 billion, Hard start). index.html?preset=<id> (for example ?preset=europe) starts one straight away, on every reload. The presets are in js/data/presets.js.

Run

Open index.html in a browser (needs internet for the map tiles and Leaflet). Or run it locally: ./play.sh starts a small server (tools/serve.py) and opens http://localhost:8000 in the browser; the airport editor saves its fixes through it. Double-clicking index.html (a file:// page) is not enough: browsers block the 3D view's modules there.

Smoke test: node tools/smoke.mjs (Node 22+, Chrome or Chromium) loads the game headless, starts an airline, flies a timetable for a month of game time, opens every section, the airport editor and the 3D view, and fails on any script error. Run it before you push.

How to play

Screen: top left ⋯ opens the menu (save, load, new game, settings with map style and layers, developer tools, exit) and the ✈ button next to it sets the game speed. The tabs in the middle of the top bar open the sections (Fleet, Airports, Slots, Schedule, Marketplace, Finance, Rivals, Log; icons only on narrower screens), and the airline, money, time and day are on its right. Every plane has a card at the bottom: hover it for where it comes from and goes to, the time left and its fuel; click to select, click again for its stats, double-click to follow it (2D or 3D). A yellow ring marks the plane you follow, with an arrow at the screen's edge when it is off screen.

Plane window: clicking a plane (on the map, in 3D or its card) opens its window, as in OpenTTD: a live 3D camera behind it (the wheel zooms), what it is doing, its speed and height, where it comes from and goes to, the time and distance left, the passengers on board and the runways it takes off from and lands on. Runways: for every airport of its day you choose which runway it takes, or Auto: the shortest runway it can use (long enough, paved where it needs that) whose end is within 45° of the day's wind, so the long runways stay free for the big planes; it takes off and lands into the wind. A choice counts at once while the plane still boards at the gate, else from its next flight there (a flight under way keeps its runways); the route lines on the map show the chosen runways. Plane stats: 📊 Stats (in its window or its Fleet card, or its card at the bottom clicked once more) opens its records, like OpenTTD's vehicle details: maker, age, value or lease, speed, range, seats, size class, the runway it needs, its running cost per block hour (more as it ages) and its crew; then flights, passengers, seats filled, revenue, flying costs, its share of the weekly lease and crew, repairs and profit for this year, last year and all time; a bar per week for the last 12 weeks (hover for the numbers); kilometres and hours flown, how often it left on time, incidents, ferry flights and its last 8 flights. A year is the calendar year in story mode, else 365 game days. 🗓 Timetable opens its timetable in a window of its own (also from a plane's row in Schedule). Every window can be moved by its title bar (also the developer tools, the airport editor and build panel, the bug report, the airport checklist and settings) and opens where it was left last time. On a phone a click shows the plane's card in Fleet instead.

Day and night: the clock at the top is the time at your home base; every airport has its own local time (its real time zone, with summer time), shown in the airport panel with sunrise and sunset, and arrivals say the local time there. The sun rises and sets where it really does: the night moves west over the 2D map, and in 3D the sky turns orange at dusk and dark at night, the ground and buildings darken, terminal windows and taxiway centre lines light up, and planes show their red and green position lights, flashing beacons, strobes and landing lights. Runways have their lights as at real airports, seen from far away (tens of km): white edge lights (yellow over the last 600 m), green thresholds, red ends, centre-line and touchdown zone lights on the big ones, a PAPI beside each end (white above the glide path, red below), and approach lights out in front where an airport has them (by its size and the runway's length: the long ones with crossbars, red side rows and the sequenced flashers that run in towards the runway). Control towers carry a red light and the airport's rotating green and white beacon. In fog or heavy rain the lights are on by day too. Terminals, towers, aprons and taxiways show from zoom 11 near the middle of the view (everywhere from zoom 12), runways from zoom 9. Settings → On the map → Day and night turns it off. The clock at the top is your home base's, but every time written out (departures, arrivals, the timetable, an airport's board) is local at that airport, as on a real timetable: a flight from Kathmandu at 07:00 leaves at 07:00 in Kathmandu. The night curfew (no departures 22:00–06:00) is in local time too, and a plane waits at an airport until morning there.

Weather: clouds drift over both maps, from fair-weather puffs to grey rain bands and thunderstorms, and the storms in the newspaper show up as real storms. It is made up but steady: it drifts east, changes over a day or two, is drier in the subtropics, wetter at the equator and colder towards the poles, in winter and at night. Zoomed in, rain, snow, fog and lightning show over the map, and a chip at the top says the weather there (also in the airport panel and the plane window). In 3D the sky greys over under cloud. Planes crab in a crosswind: the nose points partly into the wind so they still track their path, and the pilots kick it straight just before touchdown; in gusty wind and thunderstorms they bump about a little. The plane window shows the wind and the crab angle. In 3D the wings bend a little: they droop on the ground, come up as the lift builds on the take-off run (more in turns and climbs, less in descents) and flutter in the wind. Propellers and jet fans turn while the engines run. The control surfaces move too: flaps out for take-off and further for landing (panels in two parts in the wing's livery, cut out of the wing, that slide back and down so a slot opens behind it; the Concorde has none), ailerons when rolling into or out of a turn, elevators when pitching (rotation, flare) and the rudder when turning, also steering on the ground. The weather is for looks: flights don't wait for it (storm events still close airports). It is light on the computer (one half-resolution canvas in 2D, one batch of sprites in 3D, CSS for rain and snow); Settings → On the map → Clouds and weather turns it all off.

Sound: the aircraft are heard, made up as they play, with four recordings made with ElevenLabs Sound Effects (in sounds/: the jets' deep rumble at power, their screech (played faster with the fan), a jet's starter whistling up, and the wash of an airliner far away, which planes more than about a kilometre off turn into): jets whine up on the starter during the pushback, the igniters tick, the engines light and settle to idle; a burst of thrust gets them rolling on the taxiway, take-off power roars (deep, rumbling from behind, buzzing ahead of a big fan), then climb and cruise power with the air rushing past, a whoosh on the descent, power again on the approach, reverse thrust after the tyres chirp (as much as the type really has: none on a BAe 146, half the engines on an A380, flat-pitch propellers on the old Dart turboprops), and the whine running down at the gate. Turboprops buzz (two propellers a little out of tune), old ones whistle; piston radials crank, cough, catch and run rough until warm. APUs hum at the gates. You hear what you look at: zoomed in on an airport its planes, zoomed out nothing; the plane you follow (2D or 3D, or the plane window's camera) from close behind, the wing camera right by the engines with the wind, and the fly-by camera hears it pass with the Doppler drop. Engines follow the game clock, so fast-forwarded it all goes quicker; above 300× it fades out, paused it is quiet. It is off until you turn it on: the 🔇 button in the top bar, M, or Settings → Sound (with the volume). Settings → Sound also has four styles of the same engines (Standard; Deep: darker and heavier; Open: brighter with more rushing air; Soft: muffled, for long sessions) and ▶ Preview, a whole jet, turboprop or piston flight in about 40 s heard from a chase camera, also while paused, so you can compare them (a style picked during the preview changes it at once).

Main menu: the very first start asks for a style, then the main menu offers Continue, New game, Load game (the last save in this browser, or a .json save file; ⋯ → Save to file makes one) and Quick start. A loading screen stays up until the map has its tiles. The 3D view asks once whether the device is strong enough (it needs a fast graphics chip) and names the graphics chip the browser reports.

Styles (⋯ → Settings → Style, or on the start screen): Night (the classic dark look), Tycoon (bevelled grey windows with a toolbar along the top, like a 90s transport tycoon), Metropolis (light frosted panels with a round dock at the bottom, like a modern city builder), Pixel (pixel art with a tool palette, like a sprite editor) and Departure board (black and airport-sign yellow with a sign column and flip-board numbers). Each style has its own section bar and icons; the choice is kept in the browser.

On a phone: the sections are a tab bar at the bottom and open as a sheet over the map. Drag the sheet's top edge to make it taller or shorter, pull it down to close it, or tap it to switch to full height. Pinch to zoom the map; tap a plane card to select it, tap it twice to follow it. In the browser menu, Add to Home screen installs the game as an app without the address bar.

Story mode (start screen → Game → Story mode): the airline starts in a past year (1955 by default, up to 2010) with a date in the top bar. Each New Year the newspaper announces the airliners that first flew with airlines that year, from the Super Constellation and the first jets (Tu-104, Comet 4, Boeing 707) to the 747, Concorde, the A320 and the Dreamliner; they are then sold new in the Marketplace. A type stays on sale new until its real end of production and is offered pre-owned for 25 years more. Rival airlines fly the aircraft of their time, and new airlines take the place of those that went bust. At top speed a year takes about a quarter of an hour. Free play is today's world with every type on sale.

Timetables (Schedule section): each plane gets a day plan that repeats every day. Pick the route, the first departure and how many loops, then move single flights with − / + or type a time. Each slot holds one plane on the ground at a time, from landing until departure; when it is empty any of your planes can use it, and a plane that would find every slot at its destination taken waits at its gate (a timetable that plans that is only warned about). The Slots section shows every slot of an airport over the day, what stands in them right now and the arrivals and departures. Your home base always has room for your own planes: one without a running timetable parks there off the stands, without a slot, so you can always send a plane home and it never blocks the planes flying from there. A plane flying more than 12 h a day (long haul, e.g. Zurich – Las Vegas and back) gets a second crew, paid too. One round of a timetable, turnarounds included, has to fit into a day, except with 🌏 Ultra long-haul (in the timetable, step 1): then the timetable repeats every few days instead (e.g. Los Angeles – Singapore every 2 days), each flight leaving after the turnaround, the next morning where it would land in the night curfew. Only planes with the range for flights longer than half a day (a round trip that can't fit into one day) get the option; the slots are planned as if the plane stood at those times every day.

Airport categories: by their size the airports fall into four categories: small airports (size up to 1), regional airports (size 2), large airports (size 3–4) and major hubs (size 5). The airport panel and the map legend show the category, and the list of your airports is grouped by it, the biggest first. A category only names the size: prices, fees, slots and passengers go by the size itself (airports.categories in js/config.js, G.airportCategory(code)).

Slots of an airport: an airport has one slot per aircraft stand. The Slots section and the airport panel show who holds them: you, the rivals that fly there (one slot per 4 daily flights on a route, 2 more at their hub) and other airlines (a share by airport size); the rest are free to lease (upfront + weekly fee; nothing at all where you own 50 %). When none is free you can offer a holder money for one of theirs: the airport decides by your offer and your reputation (0–100: flights flown, punctuality, crashes and incidents, your shares in that airport, your home base). A rejected offer can be made again the next day; a rival that gives up a slot flies one daily flight less there.

Stand classes: aircraft and stands come in the ICAO classes A–F by wingspan (below 15, 24, 36, 52, 65 and 80 m: a Twin Otter is B, an A320 C, a 757 D, an A330 or 747-400 E, an A380 F; the market shows each type's). A stand's class is the biggest whose widest wings fit into the room it has, with headroom on both sides (3 m for A and B, 4.5 m for C, 7.5 m from D on): the room is how far the stands beside it are (and at your own airports twice how far a building beside it is). Every slot is a stand of a class, and a plane needs a slot of its class or a bigger one: a 747 does not fit into a Cessna's slot. The airport panel lists its slots by class, and you lease the class you need (a plain Lease picks the smallest free one your biggest plane fits). At real airports the map data's stands are taken as at least class C (B at small airfields), and their roomiest third as big as the airport's size stands for. In build mode the Stand tool shows the class a stand would get where the mouse is, and a stand row the class its spacing gives.

Airport size comes from what is there: at your own airports from the stands (by class) and the longest paved runway; real airports keep their size, and the stands you build there can raise it. There are no terminal upgrades any more: you build terminals and stands yourself.

1. Click an airport on the map to see its catchment, demand from your slots and its slots.

2. Lease one of its free slots (upfront fee + weekly fee), or make an offer when none is free.

3. In the Schedule tab: click the plane, pick its airports (e.g. BRN → BCN → BRN → LHR), drag the start time and Save & fly. Below the slider, one bar per airport shows when this plane stands there (orange), when your other planes do (grey) and where all your slots there are taken (red). Planes share a slot as long as they aren't on the ground at the same time. ✨ Find a time that fits tries every start time and every stop as the place the plane spends the night.

4. Watch revenue in the Log and Finance tabs. Weekly costs (aircraft lease, crew, slots) are charged every Monday 00:00. Below CHF -500k you're bankrupt.

5. Set the ticket price of each route with − / + (in the plane's card or the airport panel), from 50% to 200% of the standard fare. Cheaper tickets fill more seats, dearer ones fewer – lower the price while seats stay empty, raise it once the plane is full.

6. More aircraft: the Market tab opens the hangar marketplace with 122 types, from the Ju 52 and Twin Otter to the A380 and Concorde, each shown in the hangar. Buy new, lease (deposit + weekly rate) or buy pre-owned (new offers every Monday; older planes are cheaper but cost more to run). New planes fly a delivery flight from their factory (🏭 on the map) to your airport, e.g. Boeings from Everett or Renton in the US. Each plane gets its own crew. Big jets need a big enough airport, and away from your home base a slot of their class to stand in. Sell owned planes or return leased ones from the Fleet tab, and give a plane its own name with ✏️ next to its registration.

7. Events: strikes, storms, volcanic ash, fuel price swings, festivals, bird strikes and crashes happen at random. Each one appears as a newspaper cutout (the game pauses until you press Continue; news that comes while the game runs in a background tab waits until you are back) and active events are listed above the tabs. Strikes and bad weather ground flights, festivals boost demand, and a crash costs you the plane, compensation and weeks of bookings. A crash always starts as an in-flight emergency (engine fire, hydraulics, lost cabin pressure, gear fault, smoke in the cockpit; about 1 flight in 150) that makes the news while the plane is still in the air (⚠ MAYDAY in its status). Only 5% of emergencies end in a crash; the rest land safely at the destination and the plane is grounded for an inspection and repairs. Where a plane goes down, a fireball and flares burn for a while, visible from far away on the map too.

Modes (chosen on the start screen, also via New game): Arcade uses normal accident rates for every maker; Realistic gives Boeing aircraft a 1000% higher crash and door-panel rate (55% of their emergencies end in a crash). Difficulty: Easy (CHF 5M, +25% passengers, −15% flight costs, bankrupt below −2M), Normal (CHF 1.5M, bankrupt below −500k) or Hard (CHF 750k, −15% passengers, +15% flight costs, bankrupt below −250k). Both are set in config.js (modes, difficulties, starterAircraft).

Rules: departures only 06:00–22:00, crew max 12h block time per day (a second crew for long-haul days; a rested crew always flies one leg, however long), each route has a limited daily demand shared by all your flights on it that day. After landing a plane turns around at the gate for 15–60 minutes by its size (Twin Otter 15, ATR 72 20, A320 30, A330 40, A380 60; turnaround in config.js).

Map: the selected airport shows its catchment ring and the towns feeding it. Click a plane or a route to select that aircraft, click empty map to deselect. ⌂ zooms to your network, the layer button (top right) switches the base map (satellite by default, remembered) and toggles towns, routes and place names.

Rival airlines: about ten AI competitors (fictional, js/data/rivals.js) – flag carriers, low-cost and regional airlines, half of them based near your home airport, the rest elsewhere in the world – fly their own route networks (thin coloured lines and dots on the map, layer "Rival airlines"). On a route you share, passengers split by the seats each airline offers per day and its ticket price (C.rivals): add flights or cut your fare to win them. Every Monday they react: more flights on full routes, fewer on empty ones, lower fares where you take their passengers, and new routes – sometimes one of yours (low-cost carriers even open a base for it). The Rivals tab shows your contested routes with your share and every rival's network; route tables show competitors as coloured dots and your share. A rival can also go bust (newspaper), and its routes are gone.

Buildings in 3D have windows, glass fronts, entrance doors on the landside, hangar doors facing the apron and open car park decks, in a few styles that differ from building to building; their roofs take the colour of the satellite photo, and the walls are picked to go with it (js/facades.js).

Gates: every airport has an apron beside its longest runway, where nothing is in the way: it keeps clear of the other runways and of the real taxiways and buildings there (read off the 3D map the first time the airport is looked at in 3D from zoom 13, kept in the browser). Up to size 2 the gates are one row; from size 3 they stand on both sides of piers, so even a hub's apron is about 1 km wide. It has a terminal, gates with jet bridges (A1, A2, …) and remote stands without bridges (R1, …): from 2 gates at small airfields to 32 at hubs, and terminal expansions add more. Zoom in on an airport to see them (2D from zoom 14, 3D from zoom 12). A plane gets a free stand when it leaves for an airport, taxis nose-in onto it, parks there (the fleet card shows the gate) and is pushed back from it tail first by a tug. G.apronOf(code) has the layout, G.gateOf the stand of a plane. The stands the game lays out itself have lead-in curves from the taxi lane, white limits between them, a service road in front of the noses and jet bridges with a rotunda at the terminal, an angled tunnel and a cab at the front left door (ap.markings, bridge parts in ap.buildings).

Airports in 3D: the 3D view also draws the runways (from zoom 10), a taxiway parallel to each runway with links to the runway ends, the runway exits and the apron, and the buildings: the terminal in one of five layouts per airport, a control tower and hangars that grow with the airport's size, so a terminal expansion shows. Planes taxi along these taxiways (G.taxiwaysOf(code) has the lines, ap.buildings the buildings). Paved runways carry their paint from zoom 14: side stripes, centre line, threshold stripes, the two numbers, aiming points and touchdown zone bars (fewer on short and narrow runways). Taxiways have shoulders, a yellow centre line and holding bars before each runway; runways from 1800 m have fast exits at 30° where landing planes leave them.

Real layouts: the airports listed in js/data/layouts.js have their real aprons, terminals, hangars, towers, taxiways and stands (js/data/layouts/<CODE>.json, loaded when the airport is first needed, see js/layouts.js). There planes park on the real stands nearest the main terminal and taxi the shortest way along the real taxiways. The data is © OpenStreetMap contributors (ODbL); tools/build_layouts.html makes the files, from Overpass API downloads where there are any and else from the vector tiles of the 3D map (OpenFreeMap): there the stands are placed in front of the mapped gates. Lukla (LUA) has a file made by hand too: its real apron, taxi loops and buildings with four stands in the bays. Reichenbach (LSGR) has a file made by hand: its real taxiway and hangars, and a small apron with three stands beside the taxiway, as none is mapped (a layout file may also say "tower": false and "bridges": false). Every other airport is read off those vector tiles in the browser the first time it is needed (zoomed in on, or flown to), by js/osmairports.js, and kept in the browser (IndexedDB, the last 300 airports): its real aprons, taxiways and buildings with their mapped heights. The terminal is the building at the mapped gates, or else the biggest one beside an apron; the others beside an apron are hangars. Stands are put in front of the mapped gates and, where there are fewer than the airport could use, in rows along the terminal's apron side (nose to it), beside the taxi lanes and in rows on the other aprons. Planes may also taxi along the runway (small fields have no parallel taxiway). Only where no apron is mapped at all does the game lay the airport out itself as described above.

Terminal concepts: the game lays terminals out in the three common ways. Linear: the gates in one row along the building (up to size 2; a longer one has its remote stands across the taxi lane). Pier: on both sides of piers (from size 3). Satellite: most gates round a building that stands free on the apron, taxi lanes all round it, planes taxi round its ends (only where chosen). A terminal you build yourself (a terminal expansion) is the copy of a real one instead: the outline, stands, taxi lanes and apron of a terminal at one of the big airports (js/data/terminals.js, 76 terminals at 40 airports, made by tools/build_terminals.html from the OpenStreetMap layouts), with about as many stands as the airport's size has, turned to lie beside the runway; the tower and the taxiways to the runway are the game's. In the developer tools the terminal of the selected airport can be set to any of these (infra.style), and "Build desert examples" puts four airports into the Sahara (Gilf Kebir) that differ only in the terminal: XLI linear, XPI pier, XSA satellite, XRE copy of a real one; the same button removes them again.

Expansion preview: in the developer tools (F2), "Show expansion preview" draws in cyan where construction at the selected airport would go, in 2D and 3D: each kind of new runway with its taxiway, the runway extension, and the apron, stands and buildings of the next terminal size (G.expansionPreview(code)).

3D view: the 3D button (or V) switches the map to a 3D globe with terrain, hill shading and 3D buildings (MapLibre). Airports stand on level ground (runways straight, no bumps from old terrain, buildings or trees in the height data), except the few whose runway really slopes, such as Courchevel and Lukla. Switching keeps the place: 3D opens where the 2D map is, at the same scale, and 2D comes back where you were in 3D. Aircraft are drawn as 3D models at their real altitude, stretched when zoomed out so you can see them. Planes really fly: they push back from their gate tail first, taxi (speeding up and slowing down), accelerate down the runway, rotate and lift off, bank into turns, pitch up to climb and down to descend, flare, brake after touchdown and taxi nose-in onto their stand, stopping about 4 m short of the terminal or hangar in front of them (big planes further back on the stand than small ones). Hover a plane for its status, click it to select it. Drag with the right mouse button (or Ctrl + drag) to tilt and rotate. Cameras, as in DCS (on phones the buttons show only their icons):

• 🎥 Follow (V): the chase camera behind the selected plane. Drag (or one finger) to turn it round the plane and tilt it; it keeps that angle as the plane turns. The wheel or a pinch zooms.
• 🎬 Fly-by (B, DCS's F3): the camera waits about a kilometre ahead on the plane's way, a little to the side, and turns to keep the plane in view as it passes; then it moves on ahead. B again moves it on at once.
• 🪽 Wing (N, DCS's F4): a camera on the wing, out towards the tip, looking ahead; it pitches and rolls with the plane. N again: the other wing.

V goes back to the chase camera from the fly-by or wing camera; otherwise it switches between 2D and 3D. B and N open the 3D view if needed and take the selected plane (or the first one in the air). The camera buttons and 🛰 Satellite sit at the bottom of the 3D view. 🛰 Satellite toggles the satellite imagery (on by default); Settings → Map style sets it too (Satellite, or the map for Standard and Dark). Where the pictures are still loading, the ground is dark. The aircraft are glTF models from models/ (Flightradar24's GPLv2 models, see models/README.md); js/data/models.js says which type uses which file; six more come from FlightGear aircraft, and the Saab 340 and Saab 2000 from 3D-print models on Thingiverse. Every model stands on 3D landing gear (js/gear3d.js, sizes and layout per model in FG.data.gear): nose and main legs with their tyres, bogies on the big jets, shock absorbers, braces and gear doors; it is raised after take-off and lowered on the approach: the legs fold into the wings and nacelles and the doors shut behind them. The shock absorbers work: in the air the legs hang out at full length (the big jets' bogies tilted), at touchdown the plane settles onto them, pushing them in and bouncing back, and the main wheels give off a puff of tyre smoke. The DC-3 sits nose up on its tail wheel. The hangar marketplace shows the same models: the selected type as a live 3D model that you can turn by dragging (double-click to reset), the tiles as pictures.

Developer tools: the 🛠 button (or F2) opens a cheat panel for testing: add or set money, add any aircraft for free (delivered instantly to the chosen or selected airport, slot included), emergency / crash / damage / repair / remove the selected plane, free slots and 100% airport ownership, finish all construction, trigger or clear any world event, spawn an incident (a bird strike, smoke in the cabin, a door panel blowing out…) or an emergency (engine fire, hydraulics…) on the selected plane, place wind, and skip an hour, day or week. Every cheat is noted in the log (js/devtools.js). Wind: pick where it blows from (degrees or N…NW), its speed (0-120 kt) and how far it reaches (50-1000 km), then Place on the map (click in 2D or 3D), At the map centre or At the selected airport. It blows at every height and fades into the weather's own wind at its edge; planes crab into it and the runways there turn into it from their next flight (one already under way keeps its runways). The maps show it as a dashed circle and an arrow badge; each placed wind's direction and speed can be changed in its row, or it can be removed. Placed winds are kept in the save game.

Stands in buildings: in every layout that loads, a stand that lies in a building (a mapped gate sits on its terminal) is moved out in front of the nearest wall, nose to it, or dropped where there is no room (js/layouts.js tidy; only onto an apron, never out to the land side); stands a fix already moves or deletes are left to the fix. The runways of the big airports were checked against the map (and each change against the satellite picture): 27 that lay 20 to 60 m beside the real runway at one end are moved onto it in js/data/fixes.js (their lengths are kept), and Bern's grass runway, which was there twice, is there once.

Airport editor: in the developer tools (✏️ "Fix airports on the map", or F3) you fix airports where the map data is wrong or missing. Click the satellite picture where something is off; a window opens there: on a runway, taxiway, apron, building, stand or tower you can Redraw it, Straighten it (a taxiway becomes one straight line, an apron or building gets square corners), make part of a taxiway a Curve (click two points on it: what lies between becomes two straight legs joined by a round curve; set its angle, radius and where the corner sits, or drag the corner; it starts as the taxiway runs there), Move points (drag them; a click on the small dot between two points adds one, a right-click removes one), turn a stand or set its name and length (of its lead-in line and the pushback), change a runway's width and surface, make a building a terminal or hangar, or Delete it. Anywhere you can add a runway, taxiway (also as a curve between two points), stand, apron, terminal, hangar, building or tower, and away from other airports a whole new airport. A pad is open concrete or asphalt where planes need no taxiways: they go straight across it from where they come onto it to their stand (from the nearest taxiway or runway if none reaches it). It is taken from the mapped apron there or drawn; any apron can be turned into a pad and back. Stand row places stands evenly along a line you click (start, end): set the spacing and a name prefix, and turn them round if the noses point the wrong way. Stands added or moved with the editor are always used by the game (one slot each), on top of the ones an airport of its size uses. Where too little is mapped, the game lays an airport out itself (apron, terminal, hangars, taxiways and stands beside the runway); those can be picked too ("made up by the game"). Change or delete one and everything the game made up there becomes that airport's own fixes, to change or delete piece by piece, and the game stops making it up. The last stand stays: without one the game would make the airport up again. Adding and redrawing first look in the map data (OpenStreetMap vector tiles) and show what they found in cyan: Use it, or Draw it myself by clicking its points (snapped to the taxiways and corners already there; Shift = no snapping). Changes show at once (green = new or changed, red dashed = removed); ↶ Undo (Ctrl+Z) takes them back. Save puts them into js/data/fixes.js, which every player loads:

• on the website (GitHub Pages): sign in once with "Sign in to GitHub" and a GitHub token of yours (a classic token with the public_repo box ticked; it stays on that device). Save then commits the fixes to the repo, and the website has them a few minutes later. GitHub takes the commit only from the repo's contributors; everyone else's fixes stay in their own browser (and "⬇ fixes.js" downloads the file);
• when the game runs from ./play.sh, Save writes the file in your checkout: commit and push it. The fixes are applied whenever an airport's data loads, so every game has them, new or saved (js/fixes.js; each fix finds its element again by its shape, and a fix whose element the map data no longer has is marked ⚠).

Airport checklist: F8 (or ✅ "Check airports" in the developer tools, or the ⋯ menu, where the airport editor is too: some browsers keep function keys for themselves) lists every airport in the order to check them: the start airports first, then the world's busiest airports by flights (js/data/busiest.js), then all others by size. Click one to fly there and see its mark and note. An agent that has looked at an airport marks it 🔵 Checked; a person then looks again and marks it 🟢 Good, or 🔴 Needs work (with a note saying what is wrong) to send it back. Fix in the editor opens the airport editor beside it; Next ▶ goes on down the list, and the filters show what is left to check or to approve. The marks are in js/data/checks.js and are saved like the fixes: straight into the file under ./play.sh, as a commit on the website when signed in to GitHub (in the airport editor), else only in that browser. Agents use node tools/checks.mjs (next, mark CODE --note "…", status; same order as the game).

Bug reports: F5 (or 🐞 "Report a bug" in the ⋯ menu) opens a short form: bug, idea or other, a title and what happened. The game's details (version, browser, game date, selected plane or airport, map position and the last script errors) go with it unless you untick them. Signed in to GitHub (airport editor, F3), it becomes an issue of the repo; from ./play.sh it is written into BUGS.md; otherwise GitHub's new-issue page opens filled in (you need a GitHub account), or Copy puts it on the clipboard.

Controls: Space = pause, 1/2/3 = speed, V = 2D/3D (and the chase camera), B = fly-by camera, N = wing camera. M = sound on/off, F6 = sound mixer (or 🎚 in the ⋯ menu, or Settings → Sound): which recorded bass, roar and screech the jets play (several of each; on Auto each type gets its own, old jets a turbojet screech), how loud each part is (bass, roar, screech, whine, air, engine start, far away, APU) and the screech's pitch and speed, for all planes, jets, turboprops, pistons or one aircraft type, with ▶ to hear that type. The game keeps running in a background tab. It autosaves to the browser (localStorage; the airport layouts read off the map are kept apart, in IndexedDB).

Extending

All content is plain data:

• js/data/airports.js – add airports (size 1–5 sets slot price and fees, and with them the category)
• js/data/towns.js – add towns; they generate demand for airports within 150 km
• js/data/airports-more.js, runways.js, cities.js – generated by tools/build_data.py from OurAirports (public domain) and GeoNames cities15000 (CC BY 4.0). To rebuild, download airports.csv, runways.csv and cities15000.txt into tools/cache/ and run python3 tools/build_data.py.
• js/data/aircraft.js – aircraft types (market catalogue) and crew templates; year/endYear = first year in airline service and last year built (story mode) and optionally its flight performance (climbFpm, vLofKmh, vAppKmh, bankDeg; otherwise its category's): every type climbs, turns and approaches at its own rates
• js/flatground.js – levels the 3D terrain at airports (FG.flat): the 3D map loads its terrain tiles through fgdem://, and round every airport the runways, taxiways, aprons and what lies between them become one gently tilted plane (at most 0.6 % with a long runway), sloping back to the real hills. Steep altiports (REAL: Courchevel, Lukla, Megève, Alpe d'Huez, Méribel) keep their real slope, only smoothed
• js/ground.js – ground heights along a flight (the 3D view's terrain tiles): flights climb over the mountains, circling over a valley airport such as Lugano when the ridges are too close to outclimb, and fly a steeper glide path (up to 7°) where the final approach needs it
• js/data/story.js – story mode: a newspaper line for each new type, and the rival airlines' aircraft by era
• js/data/factories.js – where each type is built (delivery flights start there)
• js/data/looks.js – side-view shape of each type, drawn by js/hangar.js
• js/data/reversers.js – each type's thrust reversers (cascade sleeve, pivoting doors, clamshell buckets, reverse-pitch propellers, ground fine pitch or none, and on which engines): moved in 3D, heard, named in the market and plane window; they shorten the landing run (game.js brakeDecel), so a plane with them turns off at an earlier exit

js/game.js is the simulation (no DOM), js/ui.js the map and sidebar, js/view3d.js the 3D view, js/hangar3d.js the turnable 3D aircraft in the marketplace. js/models3d.js loads the 3D models and js/livery.js paints them in the airline's livery, chosen in the settings (⚙ → Livery, kept in the saved game): SWISS, Lufthansa, KLM, Delta, Ryanair, Eurowings and easyJet (js/data/liveries.js), simplified after photographs of the real ones: the fuselage in one or two colours, coloured engines (found as the round pieces beside the fuselage; a jet engine keeps a bare-metal inlet lip, a grey exhaust and its own fan, and propellers are black with yellow tips, FG.data.props), a coloured fin with a mark or a simple logo (crown, crane, harp), the title on the forward fuselage, coloured wing tips. The first livery has its hangar pictures in models/hangar/; in the others js/shots3d.js renders them in the browser. tools/liveries.html shows all of them on a few types.