I flew from the states to Europe and back at 29 and 32 weeks pregnant last year. I don't remember the total flight time, I think it was 10-12 hours one way. For me, it was completely doable, but I was very comfortable even at that stage of pregnancy. Things I did to stay comfortable-
Compression stockings- I had zero swelling until I sat on that first plane, and then my feet got pretty fat. They still swelled with the stockings, but it kept it down somewhat, and I hoped lessened the risk of a blood clot.
Lots of water
Belly support band- This also helped with the circulation in my lower limbs and helped support my lower back.
Lots of pillows- on the flight home I had one inflatable neck pillow, one regular neck pillow, a wadded up sweatshirt and an airline pillow all tucked around various parts of my body. LOL. At a minimum, I definitely needed lumbar support for any time I was sitting for more than 15 min.
I also brought my mp3 player with meditations and fun stuff to listen to and an eye mask to help me sleep. I needed a lot of rest the days after the flights, but that was probably more due to the jet lag than the exhaustion of traveling. I think you can do it if you are a generally comfortable pregnant woman, with no crazy back/pelvis issues. Good luck
