Does frequently flying cause blood clots?

Maybe. Travel thrombosis is a well-recognised problem ...Dehydration, limited movement and a stting postion all contribute to slow blood flow which leads to blood being made more coagulabel...Drinking fluids, wearing compression hose, leg exercises and walking during flight all contribute to preventing this problem.
Yes, it can. Yes, it can esp if flight is long and if pt isprone to get blood clots eg obese, on contraceptives etc.