EASYJET is at "virtual capacity point" at Belfast International Airport, according to the airline's UK country manager Ali Gayward.
And if the low-cost carrier is to further grow it operation and add more new routes, it will be dependent on the Aldergrove facility expanding or possibly even adding a new terminal.
"We consistently do a refresh of our routes network, and this year have added Venice and Valencia as well as permanently basing a sixth aircraft in Belfast, which has helped us to deliver long-term sustainable growth at the base.
"EasyJet already operates 48 per cent of all flights to and from Northern Ireland, and 73 per cent from the International Airport.
"Right now there aren't too many spaces left for us at Aldergrove, but we are working closely with the current management and new owners Vinci to see what options there are going forward."
EasyJet current carries more than 4.5 million passengers a year on 35 routes from Belfast, making it by far Northern Ireland’s largest airline.
Ms Gayward was speaking as easyJet revealed a record number of passengers, highest-ever annual load factor and a 41 per cent jump in annual profits.
It reported pre-tax profits of £578 million for the year to September 30, up significantly on the £408 million seen the previous year.
But it warned that cost pressures will continue into its new financial year, with a hit of up to £100 million expected from rising fuel prices.
It also said revenues per seat will fall in the first half, due to factors including the timing of Easter.
EasyJet said it is continuing to prepare for Brexit, having set itself up across Europe to be able to operate via airlines in the UK, Switzerland and Austria to enable ongoing flying in the EU.
Chief executive Johan Lundgren said he is "confident" flights will not be grounded in a no-deal Brexit scenario after recent assurances from Brussels, and would be able to continue uninterrupted even if the UK crashes out with no agreement in place.
He welcomed the measures, which give some long-awaited clarity over flying rights for UK planes over and into the EU amid fears a no-deal scenario could see flights grind to a halt after March 29.
He said: "The European Commission has said that in the case of a no deal, they would propose measures to protect flying rights, which the UK has reciprocated. I'm confident there would be no disruption."
He said the "bare bones" agreement comes after easyJet and fellow airlines have had regular "close contact" with the government over the issue, and had been pushing for clarity on no-deal flying plans.
He also assured that easyJet had spent two years making Brexit contingency plans, setting up a Vienna-based arm called EasyJet Europe, which will enable it to continue operating flights across the EU and domestically within EU countries regardless of the Brexit outcome.
Full-year results showed the group flew a record number of passengers, up 10.2 per cent at 88.5 million, with total revenues up 16.8 per cent to £5.9 billion.
Reported pre-tax profits rose to £445 million from £385 million the previous year.
EasyJet also booked a £112 million underlying loss from its operations at Berlin Tegel Airport in Germany.
But it admitted "disruption has been a major factor" for the group, with cancellations up significantly to 6,814 from 2,502 the previous year.
The airline industry was rocked by strike chaos over the summer as a result of air traffic control industrial action in France and Italy.