err, i am pretty sure people went to france/germany before 1974 (?) when we joined the EU.
what a load of scaremongering silliness
If you were around at that time, as I was, yes people did travel, but in nothing like the numbers they do now. For one thing there were currency restrictions which made it difficult.
Then we had our own regulatory bodies but we knowingly subsumed their functions into EU bodies. We could re-create them, but it won't happen overnight - these agreements usually take a few years.
So, if May gets her withdrawal agreement through then nothing will happen on 30th March, except that the can will be kicked down the road for a couple of years. If she doesn't then, we crash out, and current aviation agreements lapse.
I for one, am not booking flights, having been caught out by the Monarch collapse. I can't afford to throw away a few hundred pounds each time, just because wealthy Tory men decided to go into a willy waving contest.