Fed-up passengers have slammed Belfast International as "the worst airport in the UK" amid growing anger over long security queues.
This week delayed holidaymakers posted photos of their travel nightmare at the terminal, with huge crowds at a standstill at security.
The airport said it had experienced difficulties in recent months due to "unprecedented passenger numbers".
It apologised to those affected and said it was taking steps to address the issue.
Thursday morning had been "particularly challenging", it added, with security provider ICTS experiencing staffing issues. This meant not all security lanes could be opened.
Michelle Devlin (46) from Strabane said she came close to missing her 7.10am flight to Manchester on Thursday.
"When we arrived there were queues right outside the front door," she said.
"I got to skip ahead because I was with easyJet but it still took us 50-60 minutes to get from the door to the scanner. We were there just over two hours and it was very tight getting our flight.
"While we were waiting, there were constant announcements for passengers flying to London and people were running through the airport to get to the gates. It was mental.
"For anyone who had young children with them, it would have been a nightmare. I'm definitely considering going to Dublin Airport instead next time."
Belfast man Neale Owen (42) said Aldergrove was "embarrassing" and branded it the worst airport in the UK.
"I've been in every airport in the UK, and Belfast International is by far the worst," he said.
Mr Owen said on June 20 he queued for 85 minutes in security with his six-year-old son before flying out to Cyprus. "The only way this will be fixed is by building a new security hall. It needs 15 lanes, not five," he added. "When they're missing staff they can be down to just three security lanes and that creates a bottleneck.
"The problem (with expanding the security hall) means they would need to knock down retail space where the restaurant is.
"I think the only way things will change is if people vote with their feet by flying out of Belfast City Airport or going to Dublin."
David O'Reilly (30) from Antrim said he was also considering switching to Dublin.
He and his partner Chris narrowly missed the 8.45am flight to Bristol, with a number of other passengers left behind.
"The pilot told us he waited as long as he could but some passengers had to have their luggage taken off the plane," he said.
Michael Collins (65) from Killyleagh complained of long security delays earlier this year.
"The queues were so slow and I asked to speak to a supervisor," he explained.
"She said she had asked for more staff to be put on but they were refused."
The airport added that it had drafted in extra qualified staff to minimise delays and was addressing individual complaints and claims for compensation.
It said: "We would continue to appeal to passengers to arrive at the airport at least two hours before their scheduled departure times, and to pay particular attention to well-publicised advice on the items they can and cannot bring through central search."