Budget airline easyJet, which launches three new routes from Belfast International Airport next month, has said the airport was a "major contributor" to half-yearly growth.
It said it had delivered a strong first half performance and "one of its best winters ever".
Ali Gayward, easyJet UK country manager and head of Northern Ireland, said: "We are the largest airline in Northern Ireland, just short of 50% total seat capacity and over 70% at Belfast International."
Currently, easyJet has five aircraft based in Belfast with a sixth due to be added to the fleet.
The airline employs 35 flight crew for its Belfast routes. It has a policy of flying into "main airports" across its network.
From June 22, passengers will be able to fly twice weekly to Marco Polo Airport in Venice.
The following day, new routes to Valencia in Spain and Naples in Italy will take flight.
These will bring easyJet's routes from Belfast International to a total of 31. As many as 4.5m passengers fly to and from Belfast International with the airline every year.
Easyjet also operates flights to 12 UK destinations from Belfast International including three in London - Gatwick, Stansted and Luton - Edinburgh and Glasgow. During the summer, Isle of Man flights will be increased to twice a week. This decision was due to the popularity of the Isle of Man TT Races.
Mrs Gayward added: "Belfast was one of our first businesses when we launched our flights 18 years ago.
"We have been committed to Belfast all this time. Belfast has been a really major contributor to the half yearly figures - that is why we are investing in extra aircraft."
Mrs Gayward added that the airline has "room for more growth" in the future, noting that Belfast "is not a capacity constrained" airport.
"What is particularly important for Northern Ireland now is our announcement about the easyJet holiday programme which allows customers to buy an all-inclusive holiday," she said.
"The appointment of new chief executive Garry Wilson, who has joined easyJet from TUI, is going to drive easyJet holidays forward.
"Most of these passengers are flying with us but are booking hotels separately."
The company believes that booking a combined package will be "better value" for customers.
Mrs Gayward estimated that approximately 90 million passengers could be expected to avail of easyJet holidays across its network annually.
Passenger numbers for the six months to March 31 increased overall by three million to 36.8 million.
The average cost per seat, excluding fuel, increased by 2.2% to £43.
Headline profit before tax, excluding costs associated with its new operations in Berlin Tegel, came in at £8m against a £212m loss last year.
Revenue rose 19.5% to £2.18bn in the period for the first time, up almost 20% year on year.
Passenger numbers increased by three million, or 8.8%, to 36.8 million in the period, including 700,000 from Tegel.
The company indicated that easyJet adds aircraft to its fleet every two or three years at a cost of $100m each.
Its new Airbus A320neo has been designed to minimise noise impact on local communities and can achieve up to 15% savings in fuel burn and CO2 emissions.