The US Air Force is to restrict flights of its most advanced fighter jet, the F-22, following an order from the defense secretary, Leon Panetta, Pentagon spokesman George Little told reporters on Tuesday. The decision comes in response to complaints from pilots who experienced dizziness and blackouts while piloting the jets. At least a dozen F-22 pilots have reported suffering oxygen deficiency. However, it is yet unclear what exactly caused the problem. Meanwhile, Panetta has ordered that the F-22 Raptor will not be conducting long-range flights and will stay within range of runways.