. .It comes down to, "how did we manage to do xxxxxxx before the EU" and "and how do non-EU countries manage to do xxxxxxxx?" . .
How did we ever manage to have airlines fly third country routes before the EU?
We didn't
Whut? 
Prior to the EU we couldn't fly to anywhere but the UK...?
Not what I said
You couldn't embark and disembark on a UK airline between two airports in non UK countries (the Empire and later Commonwealth may be exception) And in much of the world the same still applies.
So it isn't a Brexit issue then...?
And if ROW copes it probably almost certainly isn't an issue at all...
Well it is a Brexit issue as it removes all UK airports and UK flagged carriers from those 6th and 7th air freedoms that go beyond the Chicago treaty
The ROW copes either because they have large internal markets (eg USA), free trade blocs (eg NAFTA) or in many cases whopping high prices and dodgy planes
Those that want no deal ought to be careful what they wish for
Well, there is nothing like a sweeping generalisation to secure your argument is there…?
In December I sat on the Interwebz here and bought an airline ticket with €uros from my Cyprus bank account.
In April I flew Larnaca >>> Dubai >>> Sydney >>> Auckland >>> Dubai >>> Larnaca.
You’ll note that several of those countries are outside the EU yet I suffered not ‘whopping high prices nor dodgy planes’…
And there are what, 100,000 flights per day, 36 million per year that arrive safely between the 195 countries of the world?
The problem is that remainers always assume that what the EU does is ‘best practice’. In reality, most of what the EU does is protectionism for the
28 27 which inevitably means higher prices and less choice for consumers.
What is the reason that any airline from any country (that meets relevant safety standards) shouldn't be allowed to operate to/from any other airport inside or outside the EU?