A U.S. F-22 Raptor fighter flies over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





A U.S. F-22 Raptor fighter flies alongside a KC-135 refueling plane over European airspace, during a flight from Britain to Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





U.S. F-22 Raptor fighters fly alongside a KC-135 refueling plane over European airspace, during a flight from Britain to Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





A squadron badge is seen on the uniform of a U.S. F-22 Raptor fighter pilot at R.A.F. Mildenhall in Britain, April 25, 2016. (Photo by Toby Melville/Reuters)





A pilot looks up from a U.S. F-22 Raptor fighter as it prepares to refuel in mid-air with a KC-135 refuelling plane over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





A pilot looks up from a U.S. F-22 Raptor fighter at a fuel boom as it prepares to refuel in mid-air with a KC-135 plane over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





Two U.S. F-22 Raptor fighters fly over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





A crew member looks out of a KC-135 refuelling plane as a U.S. F-22 Raptor fighter prepares to connect to a fuel line over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania April 25, 2016. (Photo by Toby Melville/Reuters)





A U.S. Navy F/A-18 launches from the USS Carl Vinson in this undated handout picture released November 1, 2014. (Photo by Reuters/US Navy)





U.S. F-22 stealth fighter jets fly over Osan Air Base in Pyeongtaek, South Korea, February 17, 2016. (Photo by Kim Hong-Ji/Reuters)





A U.S. Navy F/A-18 Super Hornet fighter prepares for take off from the USS Ronald Reagan, a Nimitz-class nuclear-powered super carrier, during a joint naval drill between South Korea and the U.S., in the West Sea, South Korea, October 29, 2015. (Photo by Kim Hong-Ji/Reuters)





A pair of U.S. Air Force F-15E Strike Eagles fly over northern Iraq after conducting airstrikes in Syria, September 23, 2014. (Photo by Senior Airman Matthew Bruch/Reuters/U.S. Air Force)





U.S. Air Force pilots with the Thunderbirds perform the calypso pass maneuver in F-16 Fighting Falcon aircraft during a practice session prior to the Gunfighter Skies air show at Mountain Home Air Force Base, Idaho, September 19, 2014. (Photo by Tech. Sgt. Manuel J. Martinez/Reuters/US Air Force)





A U.S. Navy crew member wipes a window of a F/A-18 Super Hornet fighter on the deck of the USS Ronald Reagan, a Nimitz-class nuclear-powered super carrier, during a joint naval drill between South Korea and the U.S., in the West Sea, South Korea, October 29, 2015. (Photo by Kim Hong-Ji/Reuters)





A U.S. Air Force F-22 Raptor fighter jet pilot waves before taking off ahead of the International Air and Space Fair (FIDAE) at Santiago international airport, March 28, 2016. (Photo by Ivan Alvarado/Reuters)





U.S. Navy test Pilot Tony Wilson smiles after making the first ever landing of the F-35C Joint Strike Fighter on the aircraft carrier USS Nimitz using its tailhook system, while off the coast of California, November 3, 2014. (Photo by Mike Blake/Reuters)





A U.S. Air Force F-22 Raptor fighter jet performs ahead of the International Air and Space Fair (FIDAE) at Santiago international airport, March 28, 2016. (Photo by Ivan Alvarado/Reuters)





A member of the ground crew signals to the pilot of a U.S. Air Force F-15E fighter jet before take off at Bagram air base, north of Kabul, August 10, 2009. (Photo by Oleg Popov/Reuters)





Lieutenant Colonel Jeannie Leavitt, 333rd Fighter Squadron commander, flies her F-15 fighter aircraft over the Grand Canyon en route to Nellis Air Force Base in Nevada, February 7, 2008. (Photo by Staff Sgt. Darin Moulton/Reuters/U.S. Air Force)