Ryanair has said it does not expect to lose any money when it shuts down its internet and call centre booking system for three days later this week.
The website and call centre booking systems will shut at 10pm on Friday and re-open at 11pm next Monday to allow for the introduction of a new reservations system.
Several figures in the IT industry have expressed surprise at the decision to completely shut down the system during the changeover and industry analysts have speculated that the closedown could cost Ryanair up to €30 million.
However, this has been rejected by the airline which said it was taking significant additional advance bookings and would take more after the shutdown to ensure that its bookings, passenger numbers and financial results would be unaffected.
The airline also rejected reports that it was making the changes to comply with the UK Office of Fair Trading, which had criticised Ryanair for not being quicker in introducing more transparency in its advertised fares. The OFT has taken action against several airlines for carrying misleading prices.
"This is nothing whatsoever to do with the OFT," the spokeswoman said. "The reservations system was at breaking point."
All Ryanair flights will operate as normal next weekend but new bookings cannot be made on www.ryanair.com or via a Ryanair call centre during this period. Nor will customers be able to make changes to flights or to review existing bookings during that time.
Passengers who cannot check in online during the affected period will not be charged the airport check-in fee for checking in at the airport.