Why Do Planes Fly Curved Routes? Great Circle Explained

Planes fly curved routes on a flat map because the shortest path between two points on a sphere is an arc called a great circle, which looks curved when drawn on a flat map. Wind also shapes the route.

Great circles

On a globe, a straight line between two cities lies along a great circle. When the globe is flattened onto a map, that line appears curved, bending towards the pole. This is why a flight from Pakistan to North America climbs far north over the map rather than heading straight west.

Wind and the jet stream

Aircraft flying eastbound often use the jet stream for a tailwind, while westbound flights avoid it. Airlines plan the route with the best balance of distance and wind, so the actual track can be longer in distance but shorter in time. This is why a westbound trip can take longer than the same trip eastbound.

Airways, restrictions and weather

Aircraft also follow airways, avoid restricted airspace, and avoid thunderstorms, so the path rarely matches the ideal arc.

On this site

Route pages such as Karachi to London show straight-line (great-circle) distance, and the live corridor shows aircraft along that path. Real flights vary.

General information only, not legal or safety advice. Details change; check with your airline and the relevant authority. See our editorial policy.