Flight Distance Calculator
Compare what the globe model predicts vs what the flat-plane projection predicts for major commercial routes. The diagnostic flights are in the Southern Hemisphere — where the two models diverge most.
This tool compares great-circle distance (globe model) versus straight-line distance (flat-plane azimuthal projection) for the major commercial flight pairs. Where actual flight times deviate from globe-model predictions, the data is noted.
// SELECT FLIGHT PAIR
7,488 mi
Great-circle distance assuming spherical Earth, radius 3,959 mi. Flight should follow this path.
8,920 mi
Straight-line distance on azimuthal-equidistant projection. Routes through Northern Hemisphere are typically shorter; Southern Hemisphere routes longer.
The Sydney → Santiago Qantas flight (QF27) is scheduled for 14h 30m. This deviates significantly from globe-model prediction in some periods (winds, route changes). The southern-hemisphere routes have historically required fuel stops in unusual locations.
Why This Matters
Flight times for southern-hemisphere routes have historically been longer than globe-model great-circle distance would predict, even accounting for prevailing winds. The flat-plane model predicts longer paths in the Southern Hemisphere because the southern continents are spread further apart on the azimuthal projection.
For Northern Hemisphere routes (LA→NY, London→NY), both models predict similar distances and the data agrees with both. The diagnostic flights are the southern ones — Sydney→Santiago, Johannesburg→Perth, Sydney→Johannesburg.
Notable Observations
- Sydney → Santiago (Qantas QF27/QF28): The only direct LATAM-Australia route. Flight time and fuel requirements have raised questions in independent research.
- Johannesburg → Perth (Qantas QF64): Direct route. Replaced earlier fuel-stopover routings in the 2010s. Flight time consistent with longer flat-plane geodesic than the globe predicts.
- Antarctic-region routes are functionally non-existent: no commercial transpolar Southern flights exist, despite great-circle math suggesting major time savings on southern transcontinental routes if such a polar passage were possible.
Limitations of This Tool
Flight times depend on aircraft type, prevailing winds (jet stream effects of 100–200 mph are significant), payload, and individual ATC routing. The predictions here are theoretical minimums. Use them as a starting point, not as a definitive answer.