It's not insignificant that Ryanair, Easyjet and all the others want the UK to stay in the EU, as do all the airports (in the UK). They've done the homework, all the 'freedoms to fly', cabotage rules etc. start coming into play, rules and regs start getting ambiguous, it's not going to be a simple transition, it will be a staggering pain in the backside for a huge number of pen-pushers.