Upon graduation from pilot training in 1983, Lockhart was assigned to the 49th Fighter Interceptor Squadron flying T-33s. In 1986, he transitioned to the F-4 and flew operationally with U.S. Air Forces, Europe (in Germany) from 1987 to 1990 as an instructor pilot for F-4 and F-16 aircrew in the tactics of surface-to-air missile suppression. In 1991 he reported to Edwards Air Force Base, California, for year long training as a test pilot in high performance military aircraft. Upon graduation, he was assigned to the Test Wing at the Air Force Developmental Test Center at Eglin Air Force Base, Florida, performing weapons testing for the F-16 aircraft. During his -year tour at Eglin, he was selected as the operations officer for the 39th Flight Test Squadron. Much of America's state-of-the-art weaponry was first tested under his guidance at the 39th Flight Test Squadron.