Tips for Safe Airline Travel: Sit Safely

From Yoga Journal:

Air travel may be more than just uncomfortable; it could be the cause of a serious medical condition referred to as deep vein thrombosis (DVT). DVT occurs after periods of prolonged immobility when a blood clot—usually formed in the lower leg, but sometimes beginning in the thigh or pelvis—blocks a major vein. Typically, such a clot dissolves once a traveler reaches his or her destination and walks around.
The good news is that simple movements found in some yoga postures can prevent a clot from forming. Any pose that stretches the calves, hips, and hamstrings can be beneficial by helping keep blood properly circulating in the legs.
Try this: Place your left foot on your right thigh and your right foot flat on the floor. Lean forward for a modified forward bend to stretch the hamstrings as well as open the hips and release the back. Switch leg positions and repeat.

Of course, the best way to prevent DVT is to move around as often as possible. If it’s OK to get out of your seat, you can usually find room near the back of the plane for poses like Uttanasana (Standing Forward Bend) and Virabhadrasana I (Warrior Pose I)—both of which stretch your legs and help keep DVT from arriving at your destination.

Standing Forward Bend