Firesidegl0w - do you really think that the millenium bug jsut went away and sorted itself out? Do you not realise that millions were spent by banks, airports, airlines, train companies, hospitals and many other small insitutions to fix the bug before it hit?
The reason it didn't happen, was because people took the threat seriously and planned for it. We aren't planning for this to be smooth, no deal means no smooth transition to the new systems.
I don't think the world will end, but until some arragements are made so that British planes and crew will get certified, there won't be flights. Not world ending, but annoying if you planned to holiday next Easter.
No deal doesn't mean no deal for ever more - but it does mean a difficult transition time. And 'difficult' does mean no flights, and problems with things that need to be imported until new treaties can be drawn up. (Which takes time)
France will still want to sell us champagne, they might just have to wait a few months to do it. Not the end of the world for France, hardly a problem for us to wait a bit. But not a smooth transition.
Long run I'm sure we'll get something sorted. Just might mean some people (like the OP) have a shit time trying to travel until it is, and if you need something imported, you might need to wait a bit to get it.