Air routes and great circles

Distance and course use a spherical earth of mean radius 6371.0 km (3440.065 nm) and the formulas in Ed Williams' Aviation Formulary: haversine distance, initial course atan2(sin Δλ·cos φ₂, cos φ₁·sin φ₂ − sin φ₁·cos φ₂·cos Δλ), the final course as the reverse of the course from the far end, and intermediate points for the midpoint and the map. The Formulary’s worked example, LAX to JFK, is 0.623585 radians — 2144 nm when one minute of arc is taken as one nautical mile, 2145 nm with the mean radius — at an initial course of 66°. On the WGS-84 ellipsoid distances differ by up to about 0.5 %.

Block time is an estimate: the distance at the preset’s typical cruise true airspeed, plus or minus the wind component you enter, plus a fixed allowance for climb and descent and for taxi out and in (shown on each leg). Real flights follow airways and tracks, not great circles, and are usually 5–10 % longer.

CO₂ per passenger follows the myclimate flight emission calculator’s calculation principles (2019 documentation): fuel per passenger = (a·x² + b·x + c) / (seats × load factor) × (1 − cargo factor) × class weight, with x the great-circle distance plus 95 km for detours and holding; separate short-haul (≤ 1500 km) and long-haul (≥ 2500 km) parameter sets, interpolated in between. CO₂ from fuel multiplies by 3.15 kg CO₂ per kg of jet fuel. CO₂e is myclimate’s headline figure: it adds upstream fuel production (0.54 kg per kg of fuel), aircraft production and airport infrastructure, and multiplies the CO₂ by 2 for non-CO₂ effects at altitude (contrails, NOₓ) — the most uncertain part. It is an average-aircraft estimate, not your flight’s actual figure; ICAO’s calculator, which uses airline schedules and aircraft types, typically gives lower numbers because it counts only CO₂.