Mildred Jane Doyle was born in Grand Rapids, Michigan, on 13 October 1921. In 1939 she graduated from Grand Rapids Senior High School and enrolled in Grand Rapids Junior College. While there, she earned her private pilot license through the Civilian Pilot Training Program. In the fall of 1940, Doyle transferred to the University of Michigan at Ann Arbor, where she also served in the Civil Air Patrol. She graduated in 1943 and worked briefly as a graphic designer in Ann Arbor.
Doyle enlisted in the WASP in 1943 and went to Sweetwater, Texas, for training in November. Following graduation in May 1944, she reported to Seymour, Indiana, for engine school. There she worked in the engineering hangar as a test pilot. In August of 1944, she married a fellow air force pilot. She resigned from the WASP in October of that year after hearing rumors that the program would be disbanded.
For the next year, Doyle moved with her husband to his various duty stations. In 1946, while he was stationed in Japan, she maintained her pilot license by renting a plane. The couple later settled in Ann Arbor in 1947 and had five children.