尽管保留在地面的F- 22，行政协调会认为，解封订单将不会改变空中力量的能力来执行空中优势，如警戒任务。这架F- 22仍然是对“国家安全任务定向“可用，行政协调会说。一次性批准的航班也可以由主要负责人的命令，inclduing定位航班。
Oxygen system concerns prompt F-22 stand-down
By Stephen Trimble
The US Air Force has stopped flying all Lockheed Martin F-22s for an indefinite period over concerns about a possible glitch in the onboard oxygen generation system.
The stand-down order issued on 3 May by Air Combat Command (ACC) chief Gen Will Fraser comes about six weeks after the F-22s were restricted to flying below 25,000ft due to the same problem.
The order is in effect until "further notice", the ACC says.
"The standown is a prudent measure following recent reports of oxygen system malfunction," Fraser said in a statement.
While the F-22s remain parked, investigation teams will continue to determine the cause of the malfunction, the statement added.
The ACC emphasized that the stand-down order is technically not considered a "grounding", which occurs only in response to a catastrophic technical issue. A stand-down is voluntary and precautionary.
Despite keeping the F-22s on the ground, ACC believes the stand-down order will not change the air force's ability to perform missions such as air superiority alert. The F-22 is still available for "national security directed missions", the ACC said. One-time flights can also be approve by the heads of major commands, inclduing repositioning flights.
The air force has been flying the F-22s operationally for more than five years, with more than 150 already in service. All 186 F-22s on order are expected to be delivered by early next year.
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