The only real place to stretch your legs is between decks on the ladder. You
can do it sitting down too if you adjust the rudder pedals full forward, but
stretching your legs with a numb rear end isn't as useful.

12+ hours in a fighter has to be major agony compared to flying in something
you can stand up in. The only advantage we had was that we could sit on our
G-suits on a trans-ocean crossing. A few repetitive manual inflations did
wonders for the tired butt. Constant air refuelings kept the boredoom town but
only a little