If you've ever tracked a flight from London to Los Angeles, you'll have noticed it doesn't sweep west across the Atlantic as the map suggests it should. Instead it arcs north, over Ireland, southern Greenland, Hudson Bay and the Rockies before dropping into California. The simple explanation is geometry: the Earth is a sphere, so the shortest distance between two points is a great circle route, which looks like a dramatic curve on the flat Mercator maps we're used to but is genuinely the straightest line on a globe.
Weather complicates things further. The polar jet stream pushes fast-moving winds eastward across the North Atlantic, meaning flights from the US to Europe get a helpful tailwind while westbound flights battle a headwind. Dispatchers therefore route Europe-to-America flights around the jet stream rather than through it, usually keeping them near that great circle line but adjusting daily as the wind shifts.
There's also an organisational layer most passengers never see. With no radar coverage over the ocean, aircraft flying between flight levels 290 and 410 follow designated 'North Atlantic Tracks', published daily by Gander and Shanwick centres to keep the dense flow of traffic safely separated. Westbound flights to the US West Coast often fly north of these tracks to dodge the jet stream, though if winds favour a more southerly routing, hopping on the tracks can be quicker overall despite the detour.
Money matters too, and not just fuel. Airlines pay overflight fees to the countries they cross, and Canada charges notoriously high ones for transatlantic traffic. When conditions allow, carriers may dip into US airspace or enter oceanic airspace earlier to reduce the Canadian bill — even if that adds flight time and burns extra fuel. Dispatchers ultimately weigh up four route types: minimum distance, minimum time, minimum fuel and minimum cost. It's the last one that usually wins, because it factors in fuel, fees, crew costs and potential curfew penalties. Ground distance, it turns out, means very little to an airline.
The extremes show how far from 'straight' long-haul flying can get. Since Russian airspace closed, Europe–Asia flights have swung far south or hugged the Arctic coastline, and some Japan–UK services now cross the Pacific, North America and the Atlantic instead. Singapore Airlines' record-breaking nonstops to New York fly over the Pacific or the Atlantic rather than the near-polar great circle, because riding the jet stream's tailwinds beats a shorter path every time. Qantas has hinted its planned Sydney–London services from 2027 may route via the North Pacific and Atlantic for the same reason.
Why should a traveller care? It explains why your flight time varies between trips in the same season, why westbound transatlantic legs run longer, and why the route on your seatback map looks nothing like the atlas. It's also a reminder that if you're chasing a window view, the Greenland-overflying northern routes are among the most scenic you can book.
Simple Flying