Consumer groups have criticised Ryanair for temporarily closing its website over one of the busiest weekends of the year - yet refusing to waive penalties for passengers who fail to check in online.
Europe's biggest budget carrier shut down the Ryanair.com online check-in facility at 4pm today for what the airline describes as "upgrade maintenance".
It is due to re-open at noon on Sunday.
During the time the airline is offline, more than one-third of a million passengers are booked to fly with the Irish carrier.
In 2008, Ryanair became the first airline to insist that passengers check in online and print out their boarding passes before reaching the airport. The fee for issuing boarding cards to non-compliant passengers at the airport has gradually increased. It currently stands at £60 per passenger, per flight.
Many planes are full this weekend, with sports fans heading for two European finals. Club football's most prestigious prize, the Champions' League, will be decided when Chelsea take on Bayern Munich in Bavaria tomorrow night.
Rugby's Heineken Cup final is being played at Twickenham in south-west London this afternoon between two Irish sides, Leinster and Ulster.
The Northern Ireland Consumer Council today urged the airline to waive the £60 fee, saying "The situation has been caused by Ryanair".
But the airline's spokesman, Stephen McNamara said: "There is absolutely no reason why anyone should fail to check in on time. We've been sending out reminder emails to passengers all week."
To use the website closure as an excuse for not checking in was, he said, akin to a child telling a teacher "The dog ate my homework".
Ryanair's online sales were suspended tonight, and are due to begin again at 10pm on Saturday.
In a normal 24-hour spell, the airline sells more than 200,000 tickets. Rival airlines are expected to win customers from Ryanair as a result of the shutdown, especially among passengers who need to travel urgently.
The website engineers' minds will be focussed by the fact that Ryanair reveals its full-year financial results on Monday morning.
The shine could be taken off the expected increased profits if Ryanair.com is not up and running on schedule.
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies