Darel Leetun was born on December 24, 1932, in Harvey, North Dakota. He was commissioned through the Air Force ROTC program on May 31, 1955, and went on active duty beginning May 27, 1956. Lt Leetun next completed Undergraduate Pilot Training at Laredo AFB, Texas, in May 1957, followed by gunnery training and Combat Crew Training at Luke AFB, Arizona. His first assignment was with the 55th Tactical Fighter Squadron at RAF Wethersfield, England, from July 1958 to July 1961, and then with the 478th Tactical Fighter Squadron at Cannon AFB, New Mexico, from July 1961 to October 1963. Capt Leetun next flew F-105 Thunderchiefs with the 44th Tactical Fighter Squadron at Kadena AB, Okinawa, from October 1963 to June 1966, followed by service with the 13th Tactical Fighter Squadron of the 388th Tactical Fighter Wing at Korat Royal Thai AFB, Thailand, from June 1966 until he was killed in action on September 17, 1966. He was listed as Missing in Action and was promoted through the ranks to Lieutenant Colonel until a presumptive finding of death was issued on March 12, 1975. His remains were returned to the U.S. on April 12, 1995, and he was buried at Arlington National Cemetery.

His Air Force Cross Citation reads:

The President of the United States of America, authorized by Title 10, Section 8742, United States Code, takes pride in presenting the Air Force Cross (Posthumously) to Captain Darel Dean Leetun, United States Air Force, for extraordinary heroism in connection with military operations against an opposing armed force as Pilot of an F-105 aircraft of the 13th Tactical Fighter Squadron, 388th Tactical Fighter Wing, Korat Royal Thai Air Base, Thailand, 7th Air Force, in action against the Cao Nung Highway Bridge in North Vietnam on 17 September 1966. On that date, Captain Leetun led a flight of F-105 Thunderchiefs against a heavily defended high priority target near Hanoi. Undaunted by intense and accurate flak, deadly surface-to-air missiles, and hostile MiGs, Captain Leetun led his flight through this fierce environment to the crucial target. On the bomb run, Captain Leetun's Thunderchief was hit by hostile fire, becoming a flaming torch and nearly uncontrollable; however, Captain Leetun remained in formation and delivered his high-explosive ordnance directly on target. After bomb release, Captain Leetun's plane went out of control and was seen to crash approximately 10 miles from the target area. Through his extraordinary heroism, superb airmanship, and aggressiveness in the face of hostile forces, Captain Leetun reflected the highest credit upon himself and the United States Air Force.