Ryanair passengers were left unable to check in ahead of their flights due to a "systems outage" which caused delays at airports across Europe.
Twitter users complained of "chaos" at Stansted Airport this morning, with many struggling to find their booking details online.
The airline confirmed that the outage resulted in disruption to airport check-ins and boarding.
A number of Ryanair flights arriving at Dublin Airport were delayed this morning.
Meanwhile, photographs posted on social media from Rome Ciampino airport in Italy show large queues forming at the Ryanair check-in desks.
A spokesman for Ryanair said: "This morning (September 14) we suffered a system outage which caused some short delays at airport check-in and boarding.
"The system has been restored and flights are operating as normal. We apologise for any inconvenience caused."
Many of the people who posted on Twitter complained they could not find their flight bookings on the budget airline's mobile app or website.
@ryanair we'd better be able to check in free of charge at the airport because your site won't load my upcoming trips, and i can't get through to anybody on your customer care line. #ryanair
— Marina Blake (@marinasblake) September 14, 2019
@ryanair Your booking API is broken. Unable to access upcoming bookings information. Console log has error 500s from the api #ryanair pic.twitter.com/99qsMcTAzx
— Jerome Toole (@jjjrome_) September 14, 2019
Ryanair states on its website that people who do not check-in online will be charged €55 per passenger to do so at the airport counter.
A spokesman for Stansted Airport said: "There was a short disruption to some of Ryanair's systems earlier today at Stansted.
"No other airlines have reported problems this morning."
