The U.S. Air Force is sending its top-of-the-line F-22 Raptor fighter jet across the Atlantic for the first time, showcasing its capabilities even as it remains off limits for export and its production line is threatened at home.

Three F-22s, built by Lockheed Martin Corp, are due to depart July 8 for Britain, where the aircraft will make its debut at an international air show, said 2nd Lt. Georganne Schultz, a spokeswoman at Langley Air Force Base, Virginia, home of the Air Force's Air Combat Command and the F-22 demonstration team.

The outing is "to show our NATO allies and international attendees what kind of capabilities we have with the F-22 Raptor," Schultz, of Langley's 1st Fighter Wing, said Wednesday.

The F-22 was deployed last year to Kadena Air Base on the Japanese island of Okinawa for its first operational overseas mission. Kadena is the hub of U.S. air power in the Pacific.

The Air Combat Command did not immediately respond to a question about whether the Air Force planned to explore potential international interest in the F-22 if the U.S. Congress were to repeal a law that bars its export.

A U.S. Air Force fact sheet says the radar-evading F-22 represents "an exponential leap in warfighting capabilities" unmatched by any known or projected fighter aircraft.

A single Raptor will perform at a show called the Royal International Air Tattoo on July 12 and 13 at Fairford, a Royal Air Force base in Gloucestershire, England, Schultz said.

The F-22 also will feature at the July 14 opening of the weeklong Farnborough International Air Show, an industry trade fair held once every two years outside London.

The F-22's unit cost is $142 million (71.3 million pounds), according to the U.S. Air Force. The F-22's two engines, built by Pratt & Whitney, a United Technologies Corp unit, produce more thrust than any current fighter engine, a fact sheet says.

Force officials say they need 381 of the F-22 Raptors to take out enemy air defences in advance of deploying less costly and less capable F-35s and other air power.

But the Pentagon's fiscal 2009 budget, unveiled February 4, made no provision for any beyond the already-approved 183, leaving a decision on whether to keep the F-22 line open to the U.S. president to be elected at the November 4 election.

NO U.S. PRESIDENTIAL REPRESENTATIVE

Unlike previous Farnborough shows, there will be no officially designated representative of the president of the United States this year, according to the Aerospace Industries Association, which represents U.S. aircraft makers and military contractors.

Heading the U.S. Air Force delegation will be Bruce Lemkin, the deputy undersecretary of defence for international affairs.

The U.S. Air Force is taking part in Farnborough first and foremost to show "support and appreciation" for Britain and the Royal Air Force, said Capt. Michael Andrews, an Air Force spokesman.

He said the show also provided a unique opportunity to demonstrate U.S. air power capabilities.

It will be attended by air chiefs from around the world, "offering an extraordinary venue to further USAF-to-foreign (air force) relationships," Andrews added in an e-mail reply to a query from Reuters.

The United States aims to develop options for operating with other nations' air forces.

A flagship of such interoperability is Lockheed Martin's F-35 Joint Strike Fighter, a family of radar-evading aircraft being developed by the United States and eight partners: Britain, Italy, the Netherlands, Turkey, Canada, Australia, Denmark and Norway.

The United States plans to buy 2,443 F-35s, including 1,763 for the Air Force, over the 30-year program which is just starting to produce aircraft. Core partners are projected to buy another 730.