Millions of Britons who flew across the Atlantic between two and four years ago are being invited to claim a share of more than £70 million that has been ordered to be handed over to them.

An advertising campaign begins tomorrow in six Sunday national newspapers advising people who flew on routes with British Airways and Virgin Atlantic between August 2004 and March 2006 to their right to a refund. Over the following two weeks it will extend to daily newspapers, magazines and travel websites. To add to the airlines’ embarrassment, they will also be obliged to carry the adverts in their in-flight publications.

The passengers are entitled to a refund as part of a £100 million settlement pending in California. It was secured on behalf of American and British passengers by two US law firms, which claimed that people had been overcharged as a result of the airlines conspiring to fix fuel surcharges on transatlantic flights.

Although the deal was struck by American lawyers in an American court, the bulk of the settlement has been reserved for British passengers – £73.5 million. That equates to a refund of between £4 and £20 for each return ticket and up to £10 for a one-way ticket. For frequent flyers and corporate customers, it could amount to hundreds of pounds.

The refund applies not only to transatlantic flights but also to any long-haul journey operated by the airlines between August 11, 2004, and March 23, 2006. That includes all Virgin Atlantic flights and most BA routes outside Europe.

Lawyers said that it was not uncommon to advertise the settlement of a class-action suit in the United States but this is believed to be the first time that it has been done in the UK.

The majority of the British passengers affected are still unaware of how to claim or even that they are entitled to a refund. Since the deal was provisionally approved in February, only about 1,200 businesses and 100,000 individuals have registered at the www. airpassengerrefund.co.uk website, set up to handle the claims. Anthony Maton, a partner at Cohen Milstein Hausfeld & Toll, one of the law firms that brought the case, said that the campaign is intended to reach at least 90 per cent of the passengers affected.

The airlines agreed to fund the £1.3 million campaign as part of the settlement. If British passengers fail to claim all the £73.5 million allocated to them, the airlines will be entitled to keep the difference.

Passengers have been able since February to register to receive claim forms by post or to download them. However, from July 14 people will be able to submit claims directly online. They must provide either the number of the relevant flight, their frequent flyer number or a ticket number. BA passengers can submit their passport number. The refunds are not being administered by the airlines but by an independent mediator. They will begin in October if the settlement is formally approved by a judge on September 26. There is a December 2012 deadline.

BA has been fined £270 million by the Office of Fair Trading and $300 million by the US Department of Justice after it was found guilty of conspiring to fix the surcharges. Virgin escaped financial penalties after it came forward to expose the collusion.

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