The shutdown, which is part of a system upgrade, will start at 9pm and will last for five hours. The airline said the site and app should both be operational again from 2am tomorrow.
A spokesperson from Ryanair said the upgrade is to allow for essential system maintenance to take place, in preparation for the launch of the airline’s new website this autumn.
As online check-in services will be unavailable during the five-hour window, the airline is advising passengers travelling today or tomorrow to check in for their flight and print their boarding passes as soon as possible before the site and app shuts down.
“Our online check-in service will not be available. Flight bookings and changes will also be unavailable during this period,” said Ryanair’s Robin Kiely.
“We sincerely apologise for any inconvenience caused by this upgrade, which will further improve Ryanair.com.”
The airline said it was contacting all customers intending to travel either today or tomorrow by email and text message to alert them to the system upgrade and the temporary unavailability of their services.
It has also posted notice of the shutdown on its website and on social media and reminded customers that check-in is available from 30 days up to two hours before a flight.
It said it is “each customer’s responsibility to ensure they have completed the check-in process as required”.
Meanwhile, it has emerged that Ryanair is in talks with International Airlines Group and Aer Lingus and Portugal’s TAP about providing feeder flights to rivals’ long-haul services for the first time.
The airline’s chief executive Michael O’Leary confirmed the move in an interview with Reuters. It quoted him as saying that, under the possible deal, customers would buy their tickets from Aer Lingus, which would take all responsibility for transferring baggage and dealing with any missed connections.
“We are in active discussions with Aer Lingus in Dublin, with IAG in the UK and TAP in Portugal,” Mr O’Leary said.
He said that the ‘feeders’ could start by this winter.