Wow...that's a long flight Mandy.
The longest flight I ever took was only ten hours and that was way back in the mid-seventies when I was (ugh) so much younger and my lymphedema no where near as bad as it is now.
My leg lymphedema has never had a problem due to air travel, whether it was a long or short flight. The great thing about longer flights like that is that the larger jets are generally used. In them you are much more able to stretch, move around and even take a short walk down the aisle.
There are a few pointers I would mention:
1.) Don't keep your legs at a 45 degree angle - try to stretch them out in front of you as much as possible.
2.) One thing I do periodically is to do stretch and flex exercises right there in the seat. You can flex the thigh muscle, lower leg muscles - even foot muscles while sitting. This is really helpful.
3.) Do try and get up for that short jaunt down the aisle (not like that aother really really long walk down the aisle)
4.) Some may not have to, but I do wear compression while on the flight too. The leg swelling, for me, just starts going up the second it is unwrapped or bandaged. This should help and should not interfere with circulation.
5.)My biggest nemisis is cellulitis, so whenever I take a trip, I make certain I take a pres cription bottle of antibiotics with me. that way, if there is an emergency with infection, you can start on treatment while you find where to go to get medical help.
Relx now, and enjoy the trip
Traveling and Lymphedemahttp://www.lymphedemapeople.com/thesite ... hedema.htm