A tip off by Virgin Atlantic Airways triggered an investigation into alleged airfare price-fixing by British Airways after it passed on information to Britain's Office of Fair Trading (OFT) about its arch rival, an industry source said on Saturday.

Richard Branson's Virgin approached the OFT about alleged conversations between a BA executive and one of its staff last year to sound out plans to increase fuel surcharges on long-haul flights, the source told Reuters, confirming newspaper reports.

UK and U.S. authorities this week launched a civil and criminal probe into an alleged cartel over airfares and fuel surcharges after raiding BA's offices. BA put two senior executives on leave.

American Airlines and United Airlines said they were cooperating with the inquiry but were not targets.

Virgin's tip off underscores long-time rivalry between the two airlines which peaked in 1993 when Branson accused BA of waging a dirty tricks campaign against Virgin.

Virgin, which is 51 percent owned by Branson and 49 percent by Singapore Airlines, took BA to the High Court in 1993 alleging misuse of its computerized passenger data. The case was settled out of court.

BA, Virgin, American and United are the only airlines allowed to fly direct between London's Heathrow Airport and the United States.

A BA spokeswoman declined to comment Saturday. A Virgin spokesman declined to comment but reiterated the airline was assisting with inquiries.

BA suspended its Commercial Director Martin George, one of the airline's top executives who was responsible for announcing the increases in the airline's fuel surcharges.

It also suspended its Head of Communications Iain Burns who reports directly to George.

BA Chief Executive Willie Walsh has not commented on the investigation so far.

Things are looking extremely serious. Willie Walsh has just gone to ground. BA has suddenly lost years of experience and there is a big hole to fill, the source said.

BA faces fines of up to 300 million pounds, or 10 percent of turnover on its lucrative transatlantic routes if found guilty of price-fixing, analysts said. If the probe involved the airline's total operations that could increase to 900 million pounds.

The Times newspaper said Saturday the FBI was assisting the U.S. Justice Department with the investigation and was expected to question BA executives in New York.

BA first introduced a fuel levy in May 2004 which it last raised in April this year after crude oil prices nosed above $70 a barrel. Virgin Atlantic also introduced a fuel surcharge at around the same time.

The investigation follows a price-fixing probe involving airlines' cargo charges announced in February which spread to carriers in the United States, Europe and Asia. That investigation is still proceeding.