There has been recent news concerning people not surviving the flight. When you sit for long periods of time, clots can form in your legs and in your groin area. When you stand up, you can have a stroke.

If you're flying internationally, do your best to go either Business Class or First Class. Flying from San Francisco to Hong Kong, Taiwan or Japan can be a boring flight. With the upgraded facilities, you'll be more comfortable and the food is better (I had four complete filet mignon dinners on my last San Francisco-to-Hong Kong flight). Get up once an hour and walk for a bit. If it is a 747 or higher jet, go upstairs to the lounge. Bring music (I recommend a minidisc player) and a laptop with a power adapter.