Ryanair and Aer Lingus have both announced that they will be scaling back their operations from both Belfast International Airport and George Best Belfast City Airport.
Belfast International Airport flights to destinations such as Manchester, Berlin and Lanzarote could be among those affected by the plan.
Aer Lingus has sub-contracted flights out of Belfast City Airport to Faro in Portugal and Malaga in Spain to ASL Airlines Ireland since mid-2018.
DUP MP Ian Paisley said it was his understanding that implementation of the airlines’ scaling back operations was imminent.
The UK’s Air Passenger Duty (APD) has been blamed for the airlines’ decision. APD – a controversial tax imposed on air travellers that varies depending on destination and class of travel – only applies to short haul flights from Northern Ireland.
The tax can mean up to £26 in tax on any return domestic flight.
There is no equivalent tax on flights from the Republic of Ireland.
An Aer Lingus spokesperson said: “Aer Lingus has decided to discontinue its services from Belfast City Airport to Faro and Malaga for the Summer 2020.
“The decision was made following a commercial review which determined that the routes were not performing in line with expectations. In 2020 Aer Lingus will continue to deliver a high frequency daily service between Belfast City and London Heathrow.
“In summer 2019 Aer Lingus increased frequencies on the route to 4 times daily on Tuesdays, Wednesdays, Thursdays and Saturdays.”