Want an exit seat? Go online

An "online scrum" - that is how one frequent flyer characterises British Airways' new policy on the allocation of seats, which takes effect on 5 December. The seating plan for each flight will be released on the airline's internet site, www.ba.com, exactly 24 hours before the departure time. From that instant, passengers will able to book any available seat on the plane, including emergency exits with extra legroom.

At present most short-haul passengers on BA choose seats at the airport, while many long-haul travellers are allocated specific seats months in advance. Ten days from now, a unified system will be brought in, aimed at encouraging passengers to self-allocate online before reaching the airport. "This will make the process of choosing your seat simpler and more transparent," says a spokeswoman for the airline. "We're giving control back to customers."

Travellers without access to the internet - and late bookers - will be disadvantaged by the change. They may find that they are unable to sit next to their travelling companions. On busy flights, they are likely to be confined to unpopular middle seats. Families travelling with children under 12 are exempt from choosing a seat online; such groups should be pre-allocated seats together, three days before departure. And some "commercially important passengers" will be able to book seats further in advance. Anyone who has bought a fully flexible ticket, regardless of class, will be able to choose a seat at the time of booking. So too will members of the upper levels of BA's Executive Club, holding silver or gold cards.

BA hopes the new system will reduce queues and congestion at airports, and provide greater certainty for travellers. At present, last-minute juggling of capacity at the airport can mean that passengers with pre-allocated seats are obliged to move.

"Under the new system, once you have your allocated seat it won't be changed unless there's an extreme operational reason," says a spokeswoman for the airline. Such "extreme" cases might be when flights are disrupted, or if a late change of aircraft type is made.

Long-haul rivals of BA, including Virgin Atlantic, are likely to seek to capitalise on the change by promoting the option of pre-booking seats well ahead of departure. On European and domestic flights, BA's move is aimed at gaining an edge over its no-frills competition - particularly easyJet. The low-cost operator does not allocate seats at all; passengers are allowed on board in groups of 30, in the order in which they check in. The only exceptions are for families with young children, and passengers who pay a £5 "Speedy Boarding" fee, which allows up to 20 passengers to board ahead of the pack.

BA hopes the 24-hour seat-allocation window will have particular appeal to business travellers. It remains to be seen whether passengers poising themselves to choose a seat as soon as the flight is released will put a strain on the airline's website.