An economy class seat on a flight that lasts eight hours or longer can be more than just uncomfortable. Sitting for a prolonged period in tight quarters can cause medical problems with your legs. The most common result is edema or swollen ankles/feet. Eight hours of sitting can result in your feet and ankles swelling up to more than 100 percent of their normal size. This painful and annoying condition can last for days after the flight. Fortunately, there are things you can do to avoid leg swelling on long flights.
Avoid high sodium foods and meals the day of the flight. Sodium causes people to retain fluid, and gravity and protracted sitting will cause fluid to "pool" around the feet and ankles. It will cause the internal tissues to swell and stretch the skin.
Wear compression socks for the flight. The socks control the amount of pressure exerted on the leg, with the greatest amount at the ankle. Pressure gradually decreases to the top of the sock. This promotes better blood flow and reduces swelling.
Sit with your legs uncrossed. Crossing your legs while seated constrains blood flow.
Get up and walk several times during the flight. Walk to the back of the plane, next to the restrooms or where the stewardesses load the beverage carts. Stretch up on the balls of your feet, up and down, over and over. Lift your knees, one at a time and march slowly in place. Walk up and down the aisle a few times, from one end of the plane to the other.
Perform some leg stretching exercises while you are seated. Leave the ball of one foot on the floor and raise both heels as high as possible. Hold the position for a moment, then release and repeat. Raise one leg at a time and flex the front then heel of the foot over and over, then repeat with the other foot. Raise one knee at a time and create full circles with your ankles, in a clockwise direction and then counter-clockwise.