The United Kingdom will leave the EASA, European Union Authority for aviation safety after the Brexit transition period. The UK transport secretary Grant Shapps confirmed.
Mr Shapps stated the UK membership of EASA – the body responsible for certification of the airworthiness of their planes – would end on 31 December 2020.
In an online artical from BBC (source below) the owners of British Airways said the Civil Aviation Authority lacked world-class knowledge and could not be ready in time. https://www.bbc.com/news/business-51783580
This could now potentially mean that Aviation products and designs would need to be certified more than once. The European Union Authority aviation safety is responsible for certifying commercial aircraft for service across the EU. When the UK ends its membership of EASA, it could now need to certify aircraft separately.