Q I fly quite a bit for work -- often very long-haul flights from the U.S. to Europe and Asia. I recently had a physical, and my doctor told me I'm at risk of developing blood clots if I sit in one place for too long. He said I should get up and walk around the cabin every hour or so to make sure blood isn't pooling in my legs.I have a flight coming up and I am in a window seat. I absolutely dread the thought of asking my seatmates over and over again to please let me out, especially if they intend to sleep on the flight. However, the seat map online shows no available aisle seats. Should I ask the person in the aisle seat if he or she would like to switch with me? Would the crew ask someone to change seats with me? Please let me know. I hate to be a bother, but my doctor really has me worried about this.