Ryanair has applied for an operating licence from UK regulators amid growing concern that Britain could leave the European Union without a deal on aviation.
The Dublin-based carrier submitted its application for an Air Operator’s Certificate, essentially allowing it to continue flying routes within the UK, with the Civil Aviation Authority (CAA) on Dec 21.
It said the licence may be needed in the event of a hard Brexit to ensure it can continue to run its three domestic routes after March 2019. These routes account for around 2pc of its business.
The CAA said it was impossible to say how long it would take to assess an application, but that it would be a quicker process for an already established airline than most applicants, which have none of the requirements, such as sufficient insurance, already in place.
Ryanair's decision follows a similar move in October by Hungary's Wizz Air, whose UK business expected to start flying in March 2018 with several registered aircraft.
Meanwhile UK-based airlines, such as easyJet and Thomas Cook, have started launching new bases in Europe, in order to safeguard their routes between EU states.
Fears have been mounting among airlines that the UK may be unable to agree a new aviation agreement, which would replicate existing arrangements allowing flights between all EU states, known as the EU Open Skies policy, before March 2019.
Unlike other industries, which could fall back on World Trade Organisation rules in a "no deal" scenario, the aviation sector has no underlying global framework to fall back on, which could lead to flights being grounded.
In July this year, Ryanair boss Michael O'Leary told the European Parliament that "there is a real prospect, and we need to deal with this, that there are going to be no flights between the UK and Europe for a period of weeks, months beyond March 2019.
“There is not going to be an interim agreement, there is not going to be a legal basis, we will be cancelling flights, we will be cancelling people’s holidays for summer of 2019.”