Budget airline Ryanair is to take the "almost unheard of" step of shutting down its booking system for a weekend later this month.

Neither online nor telephone customers will be able to book flights between 10pm on Friday, February 22, and 11pm the following Monday.

Ryanair, which operates 520 routes across 26 countries and is now the largest budget airline in Europe in terms of passenger numbers, has said flights will not be affected by the shutdown, designed to allow for 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's 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.

Ryanair carries more than three million Scottish passengers every year and operates flights out of Prestwick, Edinburgh, Aberdeen and Inverness airports.

Last month, the firm announced that it was to open new routes out of Edinburgh to Marseille, Pisa, Bremen, Frankfurt and Alicante.

The company, which has its headquarters in Dublin and its largest operational base at Stansted, has a highly profitable impact on Scotland. Ryanair flights are reported to have generated £140m for the Scottish economy with inbound passengers spending an average of £300.

More than one million passengers travel through Prestwick Airport every year, bringing an estimated £26m to the area. The firm operates 17 routes out of the airport and the budget airline is said to support up to 542 jobs in the Ayrshire area and a total of 3000 jobs across Scotland's tourism sector.

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 £3 airport check-in fee. Travellers who have elected to check in online 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 up on the airline's website 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.

Ryanair has been characterised by rapid expansion, a result of the deregulation of the air industry in Europe in 1997.