The airline wants to avoid disruptions to services in the change from the Accenture-owned Navitaire system, which is typically used by budget airlines, to Sabre's global distribution system.

Passengers will not be able to access Virgin's Velocity loyalty program via the internet to make a booking or redeem frequent-flyer points from 10.30pm on Wednesday to Sunday. Nor will it be possible to check in for flights via mobile phones or the internet this weekend.

Passengers will be unable to book flights via Virgin's website from Saturday until Sunday afternoon.

The airline has also warned passengers flying between next Monday and January 20 to turn up at airports at least an hour before a domestic flight and three hours before an international service because checking in might be slower than usual.

Virgin will increase staff at airports and call centres by 30 per cent this weekend to handle the complex switch in reservation systems. About 4000 Virgin staff have undergone training over the past year.

Virgin spokeswoman Danielle Keighery said on Monday that checking in for flights might be slower because of the changeover to the new IT system but the airline had measures in place to make it as smooth as possible.

The airline declined to put a figure on the ongoing cost of the more expensive Sabre system, saying only that ''there was no material difference'' to using Navitaire. It also said there would be one-off costs from implementing Sabre.

The new system will allow Virgin to better link its services to alliance partners such as Etihad and Singapore airlines, as well as making its flights more visible to travel agents around the world. The change will also result in Virgin switching its flight code from DJ to VA.

Virgin has been eager to ditch the Navitaire booking and check-in system. In 2010, the airline suffered an 11-day blackout of its reservations system.