Swelling of legs and ankles. First noticed on transatlantic flight?

No movement. If you are on a long flight and your legs are dependent, and not moving then your lower extremities can swell. The concern is that you don't have or wont develop a clot. It is always good to mention your new finding to your internist. Next time you travel, compressive socks or hoosiery can be worn. Also, try and get up on the plane every now and then to move around.
Pressure. Swelling in the legs can occur with any flight. However, the biggest concern is the development of a blood clot in the legs.