Some flights at the Dublin, Cork, Knock and Shannon airports have been cancelled as Aer Lingus pilots are due to go on strike on Saturday.
The pilots began a work-to-rule on Wednesday and the strike action, which will last for eight hours, starts at 05:00 local time.
This is part of an ongoing dispute over pay.
The Irish Airline Pilots' Association (Ialpa) previously called for a 24% pay rise for members.
The pilots' picket line will be at the entrance to Dublin Airport.
Aer Lingus say there are "a number of options" for passengers affected.
The airline has now cancelled almost 400 flights as a result of the indefinite work-to-rule and strike action by pilots.
Which Aer Lingus flights are cancelled?
The Aer Lingus website has a list of flights disrupted because of the strike.
It currently lists more than 50 cancelled flights from Dublin airport on Saturday.
Up-to-date flight information is available on the Aer Lingus flight status tool or on their mobile app.
The airline's website states that if your flight is affected, you will be contacted by them directly by email or SMS message.
Or, if you booked through a travel agent, they will contact you to advise you of your options.
Will my Belfast flight be affected?
In short, no.
The Aer Lingus website says: "Aer Lingus Regional services to and from Belfast and Great Britain, operated by Emerald Airlines, will not be affected by any industrial relations action and will operate as scheduled."
Aer Lingus Regional flight numbers are EI 3000 – EI 3999.
What do I do if my Aer Lingus flight is cancelled?
The airline has said passengers with flights booked between now and 2 July have a number of options available.
For customers who have booked directly with Aer Lingus, there is the option to change flights online.
The company said it will waive the fare difference and any service fees if rebooking for a later date.
There is also the option to request a full refund or a refund voucher, which can be redeemed within five years.
Aer Lingus say passengers who booked through third party must contact those companies directly.
Why do the pilots want a pay rise?
Capt Mark Tighe, president of Ialpa, said that the 24% increase is a "cumulative figure of inflation from 2019, our last pay rise".
Speaking to BBC News NI's Good Morning Ulster programme on Friday, Capt Tighe said in an effort to resolve the dispute, the union had said it would accept less than an inflationary rise.
"We don’t believe anybody should be getting less than inflation, but yesterday in an effort to resolve this, we said we would accept less than inflation."
However, he added: "We believe inflation is a very reasonable claim in this current time."
How much are Aer Lingus pilots paid?
Co-pilots can start out at about €36,000 (£30,400), with packages increasing based on actual flying hours.
Irish broadcaster RTÉ has reported a captain at the top of the scale can be paid about €287,000 (£242,000).
Capt Mark Tighe explained on Thursday that this can take up to 26 years.
There are differences for pilots depending on whether flights are short or long-haul.
Further strike action?
Irish broadcaster RTÉ had reported that the recommendation for an additional strike was made by IALPA on Thursday.
However, on Friday afternoon, Capt Mark Tighe said that Ireland's Labour Court has invited both parties in the dispute to return to them on Monday afternoon.
"We are in the process of discussing that and that of course would have relevance to whether or not we escalate the industrial action," he told BBC News NI.
"I’m hoping now that they have noted the seriousness of the situation and that they’ll be able to apply their considerable expertise."
How did we get here?
This has been a long-running dispute over pay, and there have been a lot of announcements.
But here are some of the key things that have happened so far this week:
- 25 June 2024 - Separate meetings between Ireland's Labour Court and Aer Lingus and the Ialpa.
- 26 June 2024 - Pilots' indefinite work-to-rule begins. (The work-to-rule means not working overtime or carrying out any other out-of-hours duties.)
- 26 June 2024 - The airline issues an invitation for talks to Ialpa on Wednesday after pilots began their work-to-rule.
- 27 June 2024 - Talks between Ialpa and Aer Lingus to resolve the ongoing pay dispute break down without a resolution.
- 28 June 2024 - Aer Lingus confirms it is cancelling a further 122 flights, saying that due to the “indefinite nature” of Ialpa pilots’ industrial action it “must cancel” additional flights up to 7 July.
- 29 June 2024 - Pilots take part in eight hours of strike action.