LONDON – British Airways PLC, American Airlines and Spain’s Iberia SA said Thursday that they have signed a revenue-sharing deal that – if approved by regulators – will see the carriers set prices together and share seat capacity on trans-Atlantic flights.

The airlines said they planned to file for worldwide antitrust immunity from U.S. authorities for the deal later Thursday. They will also notify European regulatory authorities.

The agreement is the closest alliance the three can form under strict U.S. airline ownership laws that all but rule out a full merger, and it follows two earlier failed attempts by BA and American to forge closer ties.

Gerard Arpey, chief executive of American Airlines parent company AMR Corp., thinks the deal could be approved this year.

“There aren’t any real rules or guidelines for the process, but it’s plausible it could get approved under the current administration,” Arpey said in a telephone interview.

Still, even if approval by the U.S. Department of Transportation is delayed, Arpey expects the application to be processed smoothly.

“We don’t really see any significant obstacles,” he said. “The facts are what they are, and the facts are on our side.”

Rival carrier Virgin Atlantic Airways claims the deal would seriously damage the competitiveness of the lucrative trans-Atlantic route and increase fares for passengers.

“Make no mistake, if this monster monopoly is approved it will be third time unlucky for consumers,” said Virgin Atlantic President Richard Branson. “It will still be bad for passengers, bad for competition, and bad for the U.K. and U.S. aviation industry.”

Arpey contended that the partnership would merely allow the carriers to better compete with the other major airline alliances, Star and SkyTeam, which already have antitrust immunity on trans-Atlantic flights and a large presence at other European airports.

He noted that the Star Alliance has over 80 percent of the capacity in Frankfurt, Germany, and that SkyTeam holds about 65 percent in Paris.

“All we are trying to do is put ourselves to compete more competitively,” he said. “This agreement just puts us on a level playing field.”

He said the partnership has been on hold so that other airlines could build up their presence in London, minimizing anti-competition concerns.

“We wanted to wait until the market actually demonstrated access to London so we could take the wind out of that argument,” Arpey said.

American Airlines, British Airways and Iberia are already part of the oneworld alliance, which includes Finnair and Royal Jordanian. The five carriers have 52 percent of the market at London’s Heathrow Airport.

BA chief executive Willie Walsh argued that customers would benefit from improved connections, flight schedules and frequent flier programs. He added that current high ticket prices are being driven by high oil prices, and discounted claims that fares would rise as a result of the deal.

Arpey agreed that oil prices, not the partnership, will continue to be the driver for rising ticket prices.

“American is looking to cover their costs – no company can go on charging less for their product than it costs to produce it,” he said.

Walsh also said that closer cooperation would help the airlines cut costs in the current difficult economic conditions.

“I believe this is also good news for the industry,” he said. “It’s another small step towards consolidation.”

BA and American have failed in the past to win an exemption from U.S. competition laws to work more closely together because of their dominance at London’s Heathrow Airport, where the pair have more than half the capacity to and from the U.S.

Walsh argued that the competitive situation has changed since the “Open Skies” agreement between the U.S. and the European Union came into force in March, allowing airlines to fly to and from any point in the U.S. and any point in the EU.

Walsh said he didn’t expect regulators to again insist that the carriers give up landing and takeoff slots at Heathrow – as they did in 2002 when the pair last sought antitrust immunity – and said he was confident the deal would pass muster.

“I think the environment has significantly changed,” he said, noting that some 42 airlines operate nonstop between the EU and the U.S.

Walsh argued that the Star alliance, which includes Lufthansa, United, Singapore Airlines and Air Canada, has 35 percent of the trans-Atlantic market, while SkyTeam, including KLM, Air France/KLM and Delta, has 28 percent. The oneworld alliance has 21 percent, he said.

An exemption from the anti-competition laws would allow BA and American to run their trans-Atlantic operations as a single company, with cooperation on pricing and schedules – adding to the flight capacity and airline facilities they already share in the oneworld alliance.