Some Ryanair flights in and out of Portugal have been disrupted by a strike of cabin crew based there - with further stoppages scheduled for 1 April and 4 April next week.
The airline has confirmed that it has scheduled additional flights for tomorrow morning to accommodate passengers disrupted by the strike.
However, in a statement, Ryanair declined to state precisely how many flights had failed to operate today, or how many passengers had their travel plans disrupted.
The airline reiterated that the "majority" of its Portuguese crews continued to work normally today despite a strike by its cabin crew.
Asked how many flights were disrupted due to the strike, Ryanair confirmed that a "small number" of cancellations had occurred, but would not specify how many.
Nor would it indicate how many staff it had flown into Portugal from other jurisdictions to fill in for striking cabin crew.
Ryanair described the industrial action as unnecessary and unjustified and said it was grateful to its Portuguese crews for "putting our customers first and largely ignoring this strike."
It apologised to customers and said they could be receive updates on the "Travel Updates" section of their website.
Ryanair is currently negotiating with unions across Europe after its shock pre-Christmas decision to avert pilot strikes by recognising unions for the first time since its foundation 32 years ago.
However Fernando Gandra of the Portuguese cabin crew union SNPVAC voiced frustration at the pace of negotiations, saying over 90% of Ryanair cabin crew in Portugal had backed industrial action.
He claimed that some of Ryanair's employment contracts which purported to be governed by Irish law were in breach of Portuguese law.
He said staff were concerned about issues including parental leave entitlements, and the threat of disciplinary measures if cabin crew failed to meet sales targets.
The airline has rebutted this claim, insisting their personnel enjoy among the best terms and conditions among low-cost airlines.
He noted that a third of Ryanair cabin crew in Portugal are direct employees, with two thirds hired through agencies.
Last year Ryanair flew almost 130 million passengers to and from its 87 bases across Europe, including four in Portugal.