
Make sure you do some exercise while on the airplane. Get up and walk up and down the aisle at least every hour, and wiggle your legs, feet and toes while seated to encourage blood flow. Avoid crossing your legs and make sure you wear loose, comfortable clothing.
Wear compression socks, as directed by your doctor. Compression socks are a clinically proven aid which helps direct blood flow upwards and out of danger areas. Jobst support socks can help make any long period of travel more comfortable by preventing swelling in the legs.
Finally, drink plenty of water and avoid consuming alcohol. Depending on your individual health needs, your doctor may also recommend taking blood-thinning medication such as aspirin before traveling.