Passengers walk in front of an aircraft of low-cost airline Ryanair at Weeze Airport, near the German-Dutch border, during a strike of the airline's crews, protesting the slow progress in negotiating a collective labour agreement at Weeze airport, Germany, September 12, 2018. REUTERS/Wolfgang Rattay

DUBLIN (Reuters) - Ryanair believes there is a growing risk that Britain will fail to secure an agreement on its exit from the European Union, and that aircraft could be grounded for a period of days or weeks next March as a result, its chief executive said.

“We remain concerned at the increasing risk of a hard (no-deal) Brexit in March 2019,” Michael O’Leary said in a statement published ahead of a London press conference by the airline, Europe’s largest low-cost carrier.

“While we hope that a 21-month transition agreement from March 2019 will be agreed, recent events in the UK have added uncertainty and we believe that the risk of a hard Brexit(which would lead to flights being grounded for a period of days of weeks) is being underestimated,” he said.