Defense Secretary Leon Panetta approved plans to send a squadron of Lockheed Martin Corp F-22 fighter jets to Japan, a step toward lifting flight restrictions on the most advanced U.S. warplane after the Air Force ruled out that contaminants were causing some F-22 pilots to get dizzy at the controls.

Pentagon spokesman George Little announced the decision on Tuesday, noting that a detailed and lengthy Air Force analysis had concluded that symptoms of oxygen deprivation experienced by some F-22 pilots were caused by the amount of oxygen delivered to pilots, not the quality of the air.

He said the Air Force was initiating a series of actions aimed at removing current altitude and other restrictions on the F-22 over time, and would recommend resuming most long-duration flights after the F-22 squadron flew to Japan.

The Air Force stopped flying the F-22 completely for five months last year. It resumed flights in September, but in May the Pentagon imposed new restrictions on how far they could fly from airstrips and how high they could climb.

Concern about the aircraft flared again this year after two F-22 pilots told CBS’s “60 Minutes” program they had stopped flying the fighter jet due to worries about safety.

Panetta “believes that pilot safety is paramount,” Little said. “The gradual lifting of restrictions will enable the Air Force to resume normal F-22 operations over time while ensuring the safety of the incredible airmen who fly this critical aircraft.”

Air Force Chief of Staff General Norton Schwartz said the squadron of F-22s traveling to the U.S. air base in Kadena, Japan would be accompanied by a refueling tanker, that would carry an F-22 pilot on board, who “can offer advice” in case any further incidents of oxygen deprivation, or hypoxia, developed en route.

He said the tankers would follow a flight plan that meant they were never more than an hour and a half from a landing point, and the accompanying tanker would carry enough fuel to allow the planes to reach their destination at a lower altitude

“We’re confident that we have managed the risk associated with continuing operations in the F-22,” Schwartz said, noting that modified equipment would be available in September, and it would be tested under the most demanding conditions.