If you plan on taking a long flight in the near future, you should check out these easy exercises on planes you can do to increase circulation and stay comfortable (as comfy as you can be, anyway). From airline Thomas Cook, 'Your Flying Health and Fitness Guide' is a chart that covers everything from before your flight to staying hydrated in the air and watching what you eat.
If you want to avoid sore muscles and numb legs, you might want to give some of these tips a try during your journey. Beforehand, a walk around the terminal, comfortable clothing, moderate caffeine intake and avoiding heavy meals are a good idea. Exercises on planes include the foot twirl and the neck roll.