Sorry me ol mate, you must feel like you've just logged on to a Jewish website and asked if it's OK to eat pork (no disrespect to my jewish friends)

I cannot speak from experience, having never flown in a kilt, but next time I fly there is no way I will wear trousers or even shorts.

Sitting even in a car in shorts is the most uncomfortable experience.

I would fly in a poly-vis kilt, the pleats survive sitting just fine.
On a long flight it's good to get up often and do some stretching, this will shake the pleats a bit. Anyway, who cares about a crease or two, you'll still look fantastic kilted.