AER Lingus has reported massive operating losses of €81m for the full year, compared to €20m in 2008.
The airline delayed the release of the results following the outcome of union votes on its restructuring plan.
Last week cabin crew staff voted overwhelmingly to accept the carrier's controversial €97m cost-saving plan after rejecting it earlier this month.
The union Impact said the result of the ballot was 92pc in favour of the proposals, with 8pc against, following clarifications obtained at the Labour Relations Commission (LRC).
Total revenue plummeted by 11pc to €1.2bn but Aer Lingus said in a statement that passenger figures had increased by 3.8pc to 10.4 million in a difficult year for the airline industry.
The CEO of Aer Lingus, Christoph Mueller, said the increase in the operating loss, before exceptional items, to €81m reflects the tough markets faced by the group.
But he said that the massive cost-cutting plan is vital in order to realign the cost base of Aer Lingus.
"We are satisfied that we have started the process of improving yields while implementing the necessary cost-reduction programme," he said.
"The outlook for 2010 remains uncertain with limited visibility over the second half of 2010 in particular."
Following the ballot, Aer Lingus announced it would make all 1,200 cabin crew redundant and rehire most on inferior terms and conditions and 230 would be made compulsorily redundant.
They had been the only group of workers at the airline to reject the plan.
In a statement, the airline said that although the group has experienced a slight delay in commencing certain elements of the cost-reduction programme, it nonetheless still expects to achieve staff cost savings of €40m (exit run rate of €50m) in 2010 provided there is no disruption to service over the remainder of 2010.
"Our goal for the remainder of 2010 is to position Aer Lingus for a successful future," Mr Mueller added.
The group's operating result for the first three months of 2010 is better than the prior year, according to the statement but the airline said that it is too early to comment on the full-year outlook for 2010.
The fare average for the year fell by 16.8pc on 2008, being 12pc down on short-haul fares and 15.9pc on long-haul fares.