Ryanair and Aer Lingus are both cutting routes at both Belfast International and Belfast City airports.
Ryanair has reduced a number of services at Belfast International Airport while Aer Lingus will no longer be offering two routes at Belfast City Airport from next summer.
Both airports have expressed disappointment at the flight cuts.
From November, it will no longer be possible to book Ryanair flights between Belfast and Berlin, Manchester and Lanzarote, the BBC reported.
In March, Ryanair said it was dropping routes to Poland and Malta from Belfast International, while also reducing the number of flights it operates to London Stansted and Manchester.
The carrier said this was due to the “weak UK market” and UK Air Passenger Duty.
Aer Lingus said it will no longer operate services from Belfast City to Faro and Malaga during summer 2020 following a “commercial review”.