A number of Ryanair's Portugal-based staff have been ordered to attend a meeting in Dublin later this week to face potential disciplinary action.
It follows the publication of a photo on social media, showing crew members asleep on a floor at Malaga Airport in Spain, which the airline says is fake.
The image went viral on social media.
Four Ryanair planes had been diverted due to Storm Leslie in Portugal, where they are based.
Initially, there was an apology from a member of the airline's management team.
In a tweet, Chief Operations Officer Peter Bellew apologised to the staff, saying there were no hotel rooms available on the night in Malaga.
But on Wednesday, Ryanair posted CCTV footage on Twitter, which the airline said showed that the staff involved had staged the photo.
Following the incident, a number of Ryanair employees have been asked to attend a meeting at the airline's headquarters in Dublin this week.
In a letter seen by RTÉ News, the staff in question have been told that they are "required to attend an investigative meeting under the disciplinary procedure."
The letter said the purpose of the meeting is to "discuss the circumstances surrounding the distribution on social media of a photograph" which the airline has said "faked events that occurred on October 13th".
An official with the Portuguese SNPVAC trade union, which represents the workers, said the photo was a form of protest.
Fernando Gandra said: "The image illustrated the working conditions for the crew in Malaga last Saturday night."
He added: "What we always claimed, is that Ryanair only gave the floor for people to have a rest."
Mr Gandra said he is concerned the staff involved could face disciplinary action.
In a statement, Ryanair has said "the publication of this video reveals the facts and exposes the SNPVAC union's fake news/false claims."
The statement also said the CCTV footage "proves that the original picture was staged and no crew slept on the floor."
Ryanair has called on Mr Gandra to apologise for his claim.