Gary Sigler was born in Bloomington, Illinois, in 1942. He was commissioned a 2d Lt in the U.S. Air Force through the Air Force ROTC program at Colorado State University on December 15, 1964, and went on active duty beginning January 15, 1965. Lt Sigler next completed Undergraduate Pilot Training and was awarded his pilot wings at Reese AFB, Texas, in February 1966, followed by Pilot Systems Operator training and RF-4C Phantom II Combat Crew Training at Shaw AFB, South Carolina, from February to June 1966. His first assignment was as an RF-4C pilot systems operator with the 10th Tactical Reconnaissance Squadron at Mountain Home AFB, Idaho, from July to November 1966, and then with the 11th Tactical Reconnaissance Squadron at Udorn Royal Thai AFB, Thailand, from December 1966 until he was forced to eject over North Vietnam and was taken as a Prisoner of War on April 29, 1967. After spending 2,137 days in captivity, Capt Sigler was released during Operation Homecoming on March 4, 1973. He was briefly hospitalized to recover from his injuries at Scott AFB, Illinois, and then served as a T-39 Sabreliner pilot with the 4600th Operations Squadron at Peterson Field, Colorado, from August 1973 until he left the Air Force on August 1, 1974.

His First Air Medal Citation reads:

First Lieutenant Gary R. Sigler distinguished himself by meritorious achievement while participating in sustained aerial flight as a combat crew member in Southeast Asia from 14 December 1966 to 23 December 1966. During this period, outstanding airmanship and courage were exhibited in the successful accomplishment of important missions under extremely hazardous conditions including the continuous possibility of hostile ground fire. His highly professional efforts contributed materially to the mission of the United States Air Force in Southeast Asia. The professional ability and outstanding aerial accomplishments of Lieutenant Sigler reflect great credit upon himself and the United States Air Force.