[ccmay]

It's a modified polar route that is not a great circle route.

Are you certain? For the past decade I have noticed that transatlantic flights typically have a moving-map display of real-time position and ETA that shows when there is no movie playing. I always pay attention to those maps when I fly from the Western US to Europe. If they are not great circle routes, they are pretty damn close.

Polar routes are often great circle routes; the two are not mutually exclusive. A great-circle route means that the shortest distance between any two spots on the Earth's surface lies along the line defined by an imaginary plane through those points that also intersects the terrestrial sphere in such a way as to divide it into two equal halves.

The Equator, the ecliptic, and each meridian line of longitude are examples of great circles, but there is an infinite number of great circles of varying angles of incidence and points of intersection. Any line that divides the globe into two equal halves is a great circle.

You can find great circle routes by yourself with a globe and a shoestring. Stretch the string over the surface of the globe between your origin and destination. If you do this between, say, San Francisco and London or between Paris and LA, you will be surprised at how far north the great circle will take you. That's why you can see Baffin Island and Greenland and Iceland out the plane window. It will also show you why aircraft landed at Goose Bay and Gander in the days when they did not have intercontinental range.

Perhaps you are mistaking a great-circle route for a rhumb-line route, which has been little used since the days of sextants and astrolabes, or a "small circle" defined by lines of latitude other than the Equator.

-ccm

[FreedomCalls]

Like I said, it's a modified route. The aircraft have to always be within a certain distance of a contingency airfield in case of emergency. The routes do not go too far north. The can go north of Iceland and Greenland as long as they don't go so far that they can't reach the airports there if needed. There are no commercial routes that cross over the North Pole. The Moscow-LA route stays farther south than it would if it followed a great circle route.

[Publius6961]

You are right. During many of my flights from France to San Francisco, I made careful notes when the cloud cover allowed, and easily was able to determine exact positions during flights beginning somewhat east of Newfoundland.

Comparing those position to a great circle route on a globe made it clear that they were as close to a great circle route as conditions and instruments allow. I was specially amused at the occasional corrections by the autopilot (I assume) to maintain the predefined series of rhumb lines.