Hi Mary
This has happened to me also, it is so bad we have decided to stay at home in Scotland for our holiday this year. Last year we flew an 8 hr flight to Mexico and I was in agony - I put this down to sitting in a confined space for so long.
When I travelled to Malawi in Africa on three flights adding up to 14hrs flying time I wore the flight socks when I came back to ease the pain - this certainly helped which makes me wonder whether this too is vascular.
Arlene