wear pants, there will be lots of chances to wear a kilt,there's a time and place for evrythin'.
the reasons you give are all good reasons to wear pants,you may ruin your kilt,bugger up the pleats,or spill something on it, or even trap it in the seat as you recline, maybe if you are lucky, you may even dip the back of it in the toilet on the plane, now won't that be a hoot? now if you have a ratty old kilt to travel in that you don't care about then do it. if you cherish your kilt, then wear pants.
I ,for one, don't need to be impressed.