Subject: Economy Class Syndrome
I think I mentioned the following website once before. It's How to Exercise on the Plane. Since I fly home to Sydney every year (from Toronto) I do some of these, but mostly it's just stretching my legs out in front of me (make sure you don't have your cabin luggage under the seat in front of you), make circles with my ankles, raising my feet off the ground so just the toes are on the floor and, every so often, change the position I'm sitting in (or sleeping in) ..... very easy to do and not noticable by your fellow passengers. So far, haven't had any problems. Others walk up and down the aisles on a regular basis.

http://www.thetrip.com/strategies/flight/0118.html

Marty