Aer Lingus has agreed a deal with the Dublin Airport Authority (DAA) to move the bulk of its check-in activities into the airport's new €15 million basement facility, called Area 14.

The new facility, which is situated below the arrivals area, is designed to ease congestion at the airport in advance of the opening of Pier D and Terminal 2. It can handle up to four million passengers annually, or 11,000 a day, and is expected to become operational in April.

Construction of the facility was completed before last Christmas and the DAA has been seeking a tenant since.

It is understood that Aer Lingus made a late approach to use Area 14 after long-running talks between the DAA and Ryanair broke down recently. At that stage, the DAA was considering moving long-haul operators from the US and the Middle East into the facility, a move that would have meant the former basement would have been underutilised.

Aer Lingus commercial director Enda Corneille said a deal had been agreed in principle. "This will help reduce congestion and make check-in a smoother airport experience overall," he said.

The airline said part of its operations would move to the basement facility. It will also relocate a large number of its self-service check-in kiosks.

Aer Lingus handles about six million departing passengers from Dublin each year. Some of these will continue to use the airline's existing check-in facilities.

The move will also free up space in the departures area for other airlines.

Passengers will access Area 14 through the arrivals area, check in, and then travel up two floors to departures.

DAA declined to comment, except to say an announcement would be made soon.