On a the real long flights which do allow people up and about for long periods of time, you could ask the steward/esses if it would be a problem to pray in a spot that is out of the way, if it exists.

For the most part, staying in the seat avoids being in the way, standing at the wrong times and, last but by no means least, a view of multitudes of usually immodestly dressed women. And since the point of praying is to concentrate on the prayers, usually in your seat is the best place to do that.

Those groups trying to make minyanim, gathering 10 men at the back of the plane, usually by the bathrooms, or by the service areas, that is really inappropriate for obvious reasons. Again, unless permission is granted.

And if the body is stuck in one direction, point the heart to Jerusalem.

The last liberals the world ever saw were the Egyptians who sat Joseph's brothers down and fed them meat even though they despised meat eaters. Genuine liberals tolerate the opinions of others.

Today's faux liberals do not tolerate any other opinion and if one exists it has to be squashed.