DUBLIN: Ryanair cancelled 12 international and domestic United Kingdom routes on Monday due to what it called a sudden change of Brexit-related policy by the UK Civil Aviation Authority that made their operation impossible.

Europe's largest low-cost carrier said its British arm had agreed Brexit contingency arrangements with the CAA two years ago, but that the authority had introduced new regulatory barriers on Sunday, 10 days before Britain's Brexit transition period ends.

"We are disappointed to have to cancel 12 UK domestic and international (Morocco and Ukraine) routes from London, Manchester, Liverpool, Edinburgh, Belfast and Derry, because of the CAA's unexpected policy shift late last night," Ryanair said in a statement.

"Ryanair UK had agreed Brexit contingency arrangements with the CAA 2 years ago. We call on the CAA to respect this long-standing agreement and the CAA's own established policy in order to facilitate the return of these routes as soon as possible."

The UK Civil Aviation Authority issued Ryanair UK with a UK Air Operator Certificate in January 2019, which the Irish carrier said at the time would allow it to operate its small domestic UK service and UK to non-EU routes post-Brexit.

Fellow budget airline Wizz Air also applied for a separate licence in Britain via a UK subsidiary.

Ryanair did not say in its statement what policy changes the CAA had made.

A spokesperson for the CAA could not immediately be reached for comment.