US Air Force F-22 Raptor pilots take off during the Red Flag 13-3 exercise at Nellis AFB, Nevada, on 5 March 2013. Red Flag is an advanced aerial combat training exercise usually held four to six times a year to train pilots from the US, NATO and other allied countries in realistic combat situations. The deployed Raptor pilots are assigned to the 27th Fighter Squadron at Langley AFB, Virginia.