Ryanair’s website has been hit by a second system glitch since the airline launched a new bookings system in February, causing difficulty to customers attempting to buy tickets.

It is taking customers up to a minute to switch pages on the site owing to the problems, Ryanair said, and a number of them are not receiving flight confirmations because payment authorisation is being delayed.

Some customers are also unable to check in online, leading Ryanair to waive its usual airport check-in fees while the problems are occurring.

The news follows problems experienced in February after Ryanair moved from the Open Skies booking system to New Skies, both widely used industry systems from supplier Navitaire. At the time it took down its bookings website for two days as it switched on the new system, and upon launch the website functioned slowly making some bookings difficult.

Ryanair did not disclose the exact technical issues in the current case. But on its website, it said: “Due to system problems, access to our flight booking system is currently slow.

“Please note that it may take up to 30-60 seconds to move from page to page during the flight booking process. Although the booking process is slower than normal, bookings can be completed, but the delivery of the confirmation travel itinerary may be delayed.”

It advised customers to write down their confirmation numbers from the website, rather than waiting for an email.

The airline is understood to take up to 98 percent of its bookings online, and is reliant on the system to process bookings efficiently, analysts have noted. One industry analyst said: “This problem has the potential to cost millions of pounds worth of bookings if customers go elsewhere.”

Robin Goad, analyst at competitive intelligence website Hitwise UK, said that while it could be a costly error, many of Ryanair's routes were not covered by other airlines, meaning that customers “may wait and try again”. He added: "Ryanair has a strong brand and this could help. But people have a short attention span."

Alex Bainbridge, managing director at travel e-commerce consultancy Travel UCD, said: “At this time of year, it can be a challenge for airlines because the systems need maintaining but staff are going on holiday."

"You might think the systems will stay up and running, but they are major bits of software that rely on people to keep them working, and it’s normal to experience some issues that need experts to solve.”

One analyst questioned the Ryanair's decision to launch a discount ticket promotion as soon as the new system went live in February. Shortly after launch, the booking system hit glitches and began to run slowly.

“That was a self inflicted injury,” the analyst said. “You have to be more patient and do load testing first.”

The interruption of sales can have a strong effect on seat pricing systems of airlines, Bainbridge said. The systems use algorithms to automatically set seat prices with pricing monitored by sales managers.

“Airlines estimate how many seats they will have sold, and set price ‘buckets’ for groups of seats. But when they are not taking bookings as expected, this can mean their assumptions were incorrect.”

Airlines much smaller than Ryanair sometimes even routinely take websites offline for a few hours each night to process the information, he said.

Ryanair and Navitaire have not commented on the system issues.