AER Lingus is offering refunds to customers booked on flights next week as industrial action continues to threaten its schedule.
Passengers due to travel on Tuesday or Wednesday, when pilots are set to begin industrial action, can apply to get their money back online or change their flight date for free.
A number of services will not be affected even if the action goes ahead, including regional services, the Washington to Madrid route and flights from Belfast International Airport.
There has been little progress at talks at the Labour Relations Commission to avert the shutdown in just three days.
In a message posted on its website, the airline said yesterday: "At this point in time we cannot be certain that we will be able to operate our schedule from next Tuesday."
It said customers who wanted to change their booking to a later or earlier date of travel could do so free of charge, or get a refund.
"We realise that this is extremely disruptive for our customers and we apologise most sincerely for the distress this is causing," it said.
Pilots claim they are being asked to work up to six days in a row with just one day's break due to a shortage of staff. But the airline says it has hired agency staff to make up numbers.
It also claims that the pilots are objecting to new rules that alter leave arrangements and the time they get to see the rosters.
Pilots based in Cork and Dublin airports will not report for duty until an hour later than their rostered report times from next Tuesday. They will also refuse to work on rostered free days or annual leave days.
Labour Party deputy Kevin Humphreys called on both parties to "exercise common sense".
He said an industrial dispute at the national airline could severely damage the country's reputation and economy.
"The last thing we need is a pilot strike following the positive international media attention after the state visits of Queen Elizabeth and President Barack Obama," he said.
"The Government has taken significant measures to make our tourism industry more competitive with a cut to VAT, changes in visa rules and abolition of the airport travel tax.
"Tourism is a key growth industry and has shown signs of recovery recently with passenger numbers up by 9pc in the first three months of the year."
In a tongue-in-cheek message, rival airline Ryanair, which has an almost 30pc stake in Aer Lingus, "thanked" the pilots union for a 25pc surge in late bookings for flights from Tuesday. It claimed it may be responsible for the strike after running newspaper ads last week marking 75 years of Aer Lingus strikes.
"Ryanair is starting to really warm to the IALPA union, which continues to cause uncertainty for Aer Lingus holidaymakers at peak times of the year," said Stephen McNamara of Ryanair.