Ryanair is to shut down its entire flight booking system for a whole weekend later this month, it emerged today.

Neither online or telephone customers will be able to book flights between 10pm on Friday, 22 February and 11pm on the following Monday.

Flights will continue as normal during the shutdown, which has been caused by the installation of a new booking system.

Robin Goad, research director at internet analyst Hitwise, said such a long shutdown was 'almost unheard of' for an e-commerce dependent business like Ryanair.

He said, 'It is quite incredible. Sometimes people shut things down for two or three hours. To do so for a whole three or four days is pretty much unheard of.'

Hitwise has calculated that February is one of the busiest traffic months of the year for Ryanair, and close to annual peak volumes just after the New Year.

A Ryanair spokeswoman said, 'We have already taken significant additional advance bookings, and will take more after the shutdown, which will ensure that bookings, loads and financial results will be unaffected.'

Ryanair said its free web check-in service will also not be operating during the bookings system shutdown, and that any passengers affected by this will not be charged the airport check-in fee.

Travellers who have elected to check-in on-line normally have up to two days before travelling to do so.

Access to the Ryanair destination information, travel questions, car, hotel and insurance booking facilities will be available during the weekend.

News of the internet shutdown, which is flagged on the airline's web home page, comes after gloomy trading forecast from management earlier this week.

Chief Executive Michael O'Leary warned the business could suffer from a 'perfect storm' of higher oil prices and weaker consumer demand next year.