Originally Posted by
Quokka
People shouldn't be assuming 1) that since the aircraft is past takeoff it's ok to move or 2) that FAs know squat about W&B issues.
W&B CG calculations aren't just for takeoff, they need to be within limits for the entire flight. Also realize that depending on the aircraft, its loading and use, the CG can move substantially as the flight progresses and fuel is burned. There's an NTSB report of a horrific crash where a commuter aircraft managed a takeoff but due to an out of limit CG it became uncontrollable on approach and crashed killing most on board.
Maybe from a major shift of cargo but certainly not from passengers moving seats. I can't think of a single scenario where passengers cannot move seats during flight that would affect the stability of the aircraft. Take off is a different story but after that point, you can move.