 They have also flown a number of USAF and NATO / Allied aircraft via the U.S. Navy's Personnel Exchange Program (PEP), to include, but not limited to, the USAF F-4 Phantom II, F-15E Strike Eagle and E-3 Sentry, the Royal Air Force Buccaneer S.2, Tornado GR1/GR1B/GR4/GR4A and Nimrod MR.2, and the Royal Canadian Air Force CP-140 Aurora.In all, the specific roles filled by an NFO can vary greatly depending on the type of aircraft and squadron to which an NFO is assigned.NFOs also flew in these retired aircraft, including as mission commander