After earning his Wings and Commission, Harper graduated from B-26 Transition School and B-24 Transition School. He was rated First Pilot/Aircraft Commander in the B-26, B-25, B-24 and B-17. He also flew the P-40, and flew over 100 missions as pilot of the P-63 and RP-63 in the "Pinball" Program. The RP-63 was an armored version of the P-63, and was used as a target airplane in the training of Aerial Gunners. These "Pinball" missions were flown at great risk to the pilot.
He was discharged from the Army in December, 1945 and did not pilot another airplane until 1998 - 53 years between flights - when he was invited to join the Confederate (now Commemorative) Air Force. At age 91 he now flies the AT-6, the BT-13 and the PT-19 for the CAF. He also flew the N3N, the T-34, the T-28, the Jet Provost, and he was the pilot of the only flying Curtis SB2C Helldiver in the world. He still flies in several Air Shows each year.