The collapse of the airline operator Monarch earlier this week cannot entirely be blamed on Brexit. The terror threats to Tunisia and Turkey effectively closed down the company's more profitable routes, leaving Monarch to try to earn a living on the highly competitive routes to places such as Spain and Portugal. However, the company also had to carry the increased costs of Brexit caused by the fall in the value of the pound after the referendum.
The future of the UK airline industry will be hit hard if the UK collapses out of the EU without a deal. The Open Skies policy will no longer apply to Britain and our carriers will have difficulty operating in the huge European market. Some companies have already started to shift their operations and HQ functions abroad (well done to the Brexit extremists for exporting our jobs). Air travel is a classic example of how nations need to cooperate and work together within international agreements and structures. The Brexit fantasists who believe we can simply leave the EU without a deal have not yet answered the question about how Britain will be able to continue functioning if we have been cut off from Europe. We may get the answer to that in March 2019 when it's too late to stop a slide over the cliff edge. The collapse of Monarch will simply be a bad bumpy landing in comparison.