Ryanair may have to stop selling flights to and from the UK at the end of 2018 if Britain and the EU fail to agree a post-Brexit aviation deal, according to its chief executive, Michael O’Leary.

Mr O’Leary and Ryanair’s chief commercial officer, David O’Brien, said on Wednesday that the airline was prepared for a “worst-case scenario” where the UK is no longer part of the EU’s Open Skies air transport treaty after Britain leaves Europe in March 2019.

They warned that there may be no flights between the UK and the EU, including the Republic, for a period if Brussels and Westminster have not reached an alternative agreement by the time Britain leaves the bloc.

Ryanair has plans to move aircraft that it has based at UK airports to other European locations should this happen. Mr O’Leary also suggested that it would probably have to stop selling flights between the EU and UK from December 2018.

He explained that because airlines plan their seasonal schedules months in advance, Ryanair will have to make decisions about where it bases aircraft for 2019 by the end of the previous year.

Ryanair believes a “hard Brexit” is inevitable and does not intend to increase its presence in the UK over the next two years. “We will not be basing new aircraft there in 2017 or 2018,” Mr O’Leary told a press conference.

He warned that aviation could be a pressure point in the Brexit talks as Brussels could use it to drive home the full consequences of leaving the EU on UK citizens, whom he said might end up taking their 2019 summer holidays in Scotland instead of Spain.

The point of Brexit

If the UK wants to stay in Open Skies, it would have accept both European Court of Justice rulings and freedom of movement, neither of which it is prepared to do. Mr O’Leary argued that if it backtracked on these issues to remain part of the air-transport regime, the UK would have to question the point of Brexit in the first place.

The alternative to Open Skies is to negotiate a bilateral agreement with Brussels. Mr O’Leary pointed out that in this case, the UK may still have to accept freedom of movement and that such a deal would be subject to the approval of 26 other EU member state parliaments.

He said that he had raised this with the UK transport secretary, Chris Grayling, and his cabinet colleagues but they do not accept his argument. “But if you ask them what their plan B is, they don’t have a plan B,” he added.

“They say that they cannot see how European airports are going to survive without British passengers – well, they can survive because they are going to have to.”

He argued that the UK and its government were “deluding themselves” that they could get a good Brexit deal. Instead, his company believes that Brussels is going to take as a hard a line as possible as it does not want other countries following suit.

Ryanair began offering connecting flights on its network through Rome Fiumicino Airport last week and will roll it out to other bases if it succeeds. Mr O’Brien said that it had the potential to open up large numbers of new routes.

“For example if you take Bergamo [near Milan], we have identified 300 new routes that could be created from an airport that practically did not exist a few years ago,” he said.

The airline is working on facilitating passenger transfers between its services and rivals Aer Lingus and Norwegian Air. It has recently restarted talks with Portugal’s Tap on a similar deal.