Leaving the EU would allow the UK to leave the Common European Aviation Area (AEC), a single market for commercial air transport, but could negotiate a number of different future relations with the EU.  British airlines would continue to be allowed to operate in the EU without restrictions and vice versa. The UK Government wishes to continue to participate in the European Aviation Safety Agency (EASA)  The UK has concluded its own air agreements with 111 countries that allow flights to and from the country and 17 other countries through EU membership.  These have been replaced in the meantime. Ferries will continue to operate, but with obstacles such as customs controls.  New ferry links between the Republic of Ireland and the European continent have been introduced.  In August 2020[update], the government`s Goods Vehicle Movement Service, an essential computer system for goods movement after Brexit, was still in the initial beta testing phase, four months before the operation.  If the United Kingdom does not request an extension beyond 2020, trade relations will be governed by any agreement or World Trade Organization rules from the beginning of 2021. Brexit came when the UK left the European Union on 31 January 2020.
The British Parliament adopted the European Union (Withdrawal) (No. 2) Act 2019, which received approval on 9 September 2019, and obliged the Prime Minister to seek a third extension in the absence of an agreement at the next European Council in October 2019.  In order for such an extension to be granted if requested by the Prime Minister, it would be necessary for all other EU heads of government to give their unanimous consent.  On 28 October 2019, the third extension was agreed by the EU with a new withdrawal period until 31 January 2020.  The “day of withdrawal” of UK legislation was then amended by a legal instrument on that new date on 30 October 2019.  At the end of November, EU leaders approved a draft 585-page divorce agreement and a political statement on post-Brexit relations. The bill had only been widely condemned weeks earlier by anti-Brexit supporters and lawmakers in the British Parliament. Brexit minister Dominic Raab resigned along with several other ministers, and dozens of members of the Conservative party tried to trigger a no-confidence vote in May. On 20 March 2019, the Prime Minister wrote to the President of the European Council, Mr Tusk, to tell him that Brexit should be postponed until 30 June 2019.
 On 21 March 2019, May presented her case at a European Council summit in Brussels.