Operating profit at Belfast City Airport rose 11.9% to £3.3m last year, new accounts show.
Turnover at the airport also increased 3.9% to £22.1m over the year.
The improving financial figure came despite a fall in the number of passengers using the airport during the period.
According to the Civil Aviation Authority (CAA), 2.51 million passengers passed through the terminal last year. That compared with 2.56 million during 2017 - a fall of almost 50,000.
CAA data released last week ranked Belfast City as the UK's most punctual airport.
Scheduled and chartered departures from Belfast City were delayed by an average of eight minutes - the lowest of 24 major airports in the UK.
The accounts cover the launch of a £15m investment programme at the airport.
City Airport said the scheme would enhance the experience of its core business and leisure passengers.
It includes a major upgrade of the departure lounge and an increase in the airport's retail and food and beverage offering.
Recent upgrades include an overhaul of the security area, where the average processing time has been cut to six minutes.
Chief executive Brian Ambrose said 2018 had been another strong year for Belfast City Airport.
"It was particularly pleasing to open our new security area as part of our overall terminal upgrade, which has been hugely popular with our passengers," he added.
"Our programme of investment works carry on throughout 2019 as we continue to improve the journey from car to gate.
"A covered walkway has recently been installed from our premier car park and our front-of-house area is being redeveloped, ensuring ease of access for all passengers.
"We also constantly work to develop our route offering, alongside our airline partners Aer Lingus, British Airways, KLM, and Flybe, seeking new opportunities to increase frequency and capacity across our domestic and European network."