Some calculators report the flight distance they calculate. Surely on this basic point they must all agree? Not quite. In their defence, it turns out that calculating the shortest path around the surface of an ellipsoid isn't straightforward. Moreover, the plane won't fly exactly on that line. Detour and holding pattern distances may or may not be included in the estimates reported here. Still, once again the variety in answers is surprising.
The table below shows the distance estimates for several emission calculators, in addition to some distance calculators, for a few different routes. The distance calculators are very much in sync. The emission calculators less so. Still, the largest variation here is well within 10%, making flight distance relatively well defined in comparison to the multiplicative factors involved with seating class or radiative forcing.
| Calculator | ZRH to PVG | ZRH to LHR | ZRH to CPT | ZRH to JFK |
|---|---|---|---|---|
| atmosfair | 9,078 | 835 | 9,161 | 6,355 |
| C-Level | 9,024 | 778 | 9,106 | 6,333 |
| Carbonfund | 9,051 | 793 | 9,163 | 6,346 |
| ClimateCare | 9,031 | 788 | 9,110 | 6,309 |
| ClimateCare - ANZ | 9,031 | 788 | 9,110 | 6,310 |
| FlyGreen | 9,031 | 788 | 9,110 | 6,309 |
| ICAO | 9,028 | 785 | 9,102 | 6,305 |
| myclimate | 9,000 | 800 | 9,100 | 6,300 |
| myclimate-lufthansa | 9,000 | 800 | 9,100 | 6,300 |
| myclimate-swiss | 9,000 | 800 | 9,100 | 6,300 |
| gcmap | 9,051 | 790 | 9,075 | 6,326 |
| greatcirclemapper | 9,051 | 790 | 9,074 | 6,326 |
| greatcirclemap | 9,051 | 790 | 9,075 | 6,326 |
Calculators accessed 2019-09-07.