An on-board software problem forced the Air Force's F-22A Raptors to make a return flight to Hawai'i on the fighter's first deployment outside the United States, the service said yesterday.

While en route to Kadena Air Base in Okinawa Saturday, a navigation software issue was discovered, said the 13th Air Force, which has its headquarters at Hickam Air Force Base.

All aircraft, which had departed Hickam earlier that day, returned safely. Officials expect the 12 aircraft to depart Hickam within the next several days.

"This is a minor issue, and, since our focus is always on safety, the aircraft will not depart until we are confident there are no further issues with the navigation system," said Lt. Gen. Chip Utterback, 13th Air Force commander.

The Air Force said it's deploying the dozen Raptors and more than 250 personnel from the 27th Fighter Squadron out of Langley Air Force Base, Va., to Kadena as part of a regularly scheduled U.S. Pacific Command rotational assignment of aircraft.

F-22A engineers and maintainers are working to update the software. After successful testing, the aircraft will continue their planned first overseas deployment to Kadena, the Air Force said.

The stealthy Raptors last week made their first stop in Hawai'i on their way to Japan. The Air Force plans to base 20 of the fighter aircraft at Hickam starting in late 2010.

The Raptors can reach supersonic speed without afterburners, are highly maneuverable and are practically invisible to radar.

The Hawai'i Air National Guard will be the first Guard unit to "own" the fighters; the active duty Air Force at Hickam will be an associate unit and also fly and maintain the aircraft.

Reach William Cole at wcole@honoluluadvertiser.com.