But it's hollow, and they're only doing it while they can because when Article 50 gets invoked in 2017 (Thank you Theresa for being sensible and taking your time with it) things will change massively.
Nobody has denied that many things will change as a result of Brexit. But you appear to presume that all changes will be detrimental. That is clearly not the case. Many of the forthcoming changes will be very positive for UK plc. None of us can know the future with certainty, but there's no need for an atmosphere of alarmism and slashing of wrists. And we cannot presume that the alternative road to undemocratic federal integration and eventual membership of the flawed Euro / Schengen area would have been a basket of roses either. The status quo was never an option. There are at least two ways of looking at this, and that is why we needed a referendum.
This works both ways within the industry too. The pound has fallen 10% and UK holidaymakers have less to spend abroad ... but for foreigners UK holidays just got a whole lot cheaper. Manufacturers love the implications of a weaker pound for their exports. Fuel prices (set in USD) have risen due to the weaker pound, but UK carriers pay many of their expenses in pounds yet make much of their income in foreign currencies. Airlines such as RYR and EZY would presumably prefer not to face the uncertainties deriving from Brexit, but to suppose that their overseas bases don't face challenges of their own is fanciful. Insolvent banks, further Euro bailouts, terrorism, endemic strikes (France?), oppressive bureaucracy - all will affect the market. The airlines will ultimately place their aircraft where the market is regardless of all the short-term bluster and political rhetoric. If all else fails, remember that Britain is the fifth largest economy in the world and it is a geographically compact island-nation. There will always be an opportunity for well-managed airlines to prosper here.