Too many posters are looking at the minutiae without considering the much bigger picture of the requirements of the regulation of aircraft manufacturing and aviaton services. If you read no more, please read pages 20 and 21 of this Royal Aeronautical Society document. The UK needs either to remain a full member of EASA or seek associate membership like Norway and several other countries.
Our politicians seem hellbent on seeking a 'so-called freedom' without considering the problems and costs that the aviation industry will have to bear.
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https://www.aerosociety.com/media/67...ter_brexit.pdf