Presets
Playback
Route and aircraft
Pick two of 28 airports and a generic aircraft type.
Load
Passengers, cargo and tanker fuel decide mass, CG and range.
Flight settings
Cruise level, temperature and the weather day.
Economics
Fares and fuel price.
Layers
Model checks
The science
Great circle
The shortest path on a sphere is an arc of a great circle. Distance comes from the haversine formula, d = 2 R asin( sqrt( sin^2(dlat/2) + cos(lat1) cos(lat2) sin^2(dlon/2) ) ) with R = 6371 km. On a flat map the straight dashed line is longer than the curved great circle.
Fuel burn: the Breguet range equation
For constant true airspeed V, specific fuel consumption c and lift-to-drag ratio L/D, Range = (V / (c g)) (L/D) ln(m0 / m1). The page integrates the burn in 40 km steps, with the real cruise state at every step: ISA atmosphere, drag polar CD = CD0 + CL^2 / (pi e AR) plus wave drag near the design Mach, step climbs to the weight-optimal flight level, and wind along the track. The closed form and the integration are compared in the checks.
Winds, storms and reserves
A procedural jet-stream model gives westerlies peaking near 43 degrees latitude and FL340 with drifting meanders; flying west costs more fuel than flying east. Storm cells are decorative here; the planner does not route around them. Reserves follow a simplified ICAO recipe: 5 % contingency, a 200 nm alternate at FL250 and 30 minutes of holding.
Weight and balance
Mass and moment are summed over the empty aircraft, passenger zones, cargo slots and fuel. CG in percent of the mean aerodynamic chord is (x_cg - x_LEMAC) / MAC; the allowed window narrows from 16-36 % at the empty weight to 21-31 % at MTOW (a simplified envelope). The hold is loaded by a greedy algorithm that puts heavy containers where they move the CG toward 26 % MAC.
Economics
Fare is 55 + 0.113 d dollars times the multiplier; load factor falls with price elasticity. Costs are fuel, crew, maintenance, lease, landing and navigation fees, and handling. Carrying extra tanker fuel costs a burn penalty (about 15 % of its price per flight here).
Honest simplifications
Aircraft are generic, with figures typical of their class; no real airline or type is modelled. Winds are procedural, not real forecasts; no air-traffic routing, no oceanic tracks, no real airport weather. Check-box values are model results, not flight-planning advice.
What to try
- Fly JFK-LHR, then LHR-JFK: the westbound trip burns noticeably more fuel because of the jet stream (toggle it off to see the still-air number).
- Choose "Too far for this aircraft" and read why dispatch says NO GO; the payload-range chart shows the dot outside the curve.
- Load 18 t of cargo and watch the CG dot in the envelope plot.
- Bow the route north or south: longer ground track, different winds.