Passengers at Dublin airport experienced some delays early yesterday due to new security arrangements, but queues for scanning areas later eased.
The length of time spent in queues was reduced from 1½ hours at times on Sunday when many charter flights departed to about 15 minutes yesterday.
Aer Lingus yesterday opened its check-in desks at 4am, which is an hour earlier than usual.
A spokeswoman said normally the airline opened check-ins at 5am, but had changed it to facilitate early-morning passengers going through at peak times. The airline intended to continue the earlier check-in throughout the summer.
She said they were also ensuring that check-ins were opened up to allow passengers to check-in 90 minutes before the flight, which the Dublin Airport Authority (DAA) was recommending.
The 50 Aer Lingus self-service check-in kiosks would be open from 3.30am, which was the normal summer schedule, she added.
Ten flights were delayed by 10 to 25 minutes during the peak time of 6.30am and 8.30am.
Ryanair's chief executive Michael O'Leary called for an end to the monopoly of the DAA.
"The security queues at Dublin airport are reminiscent of the queues for taxis in central Dublin prior to the deregulation of the taxi market. The solution at Dublin airport lies in opening up the Dublin airport monopoly to competition. This dithering Government has directly caused this congestion as a result of three years dithering on its promise to introduce an independent terminal at Dublin airport."
He said the recent proposal by the DAA to build Pier D would merely add to the present congestion. Pier D, which would not be a competing terminal, would force another 10 million passengers per annum through the already congested security points.
A Ryanair spokeswoman said the airline's check-ins opened two hours before the departure time.
A DAA spokeswoman said queues had shortened and passengers did not have to wait so long. Although there were some delays on the early flights, it was a great improvement on Sunday.
Fine Gael parliamentary party chairman Tom Hayes TD said people who missed their flights through no fault of their own should seek compensation. He would be raising the matter in the Dáil this week.