Ryanair have been raising a few interesting point recently, they obviously feel there are real concerns regarding the EU Open Skies Policy when they are focusing their growth away from UK which is a major market for them and looking to other EU airports.

http://www.independent.co.uk/news/business/news/brexit-ryanair-flgits-europe-grounded-uk-leave-eu-travel-industry-trade-deals-a7655226.html

This comes on top of earlier warnings that Airlines might have to move their HQ if they wish to have access to European Flight Routes

http://www.independent.co.uk/news/business/news/ryanair-easyjet-brexit-uk-airlines-move-eu-europe-lose-major-flight-routes-a7643506.html