Captain McElvain flew the Nieuport 28 as a WWI fighter pilot, assigned to the 27th Aero Squadron, 1st Pursuit Group under the command of Major Harold Hartney. He flew numerous combat missions out of air bases in France from early 1918 until August 1st of that year. On that date he was taken captive after a dogfight over Germany. He remained a POW until the armistice.
In the 1930’s, he joined the Illinois Air National Guard, and rose to the rank of Colonel and Commanding officer of the Chicago Midway based 108th Observation Squadron. His unit was activated shortly after Pearl Harbor, and he served in WWII at duty stations in Panama, Guatemala, and Okinawa.