Between 1946 and 1947, passenger airlines serving Detroit moved from Detroit City Airport on the city's crowded east side, to Willow Run; shortly thereafter, Wayne County officials began expanding Detroit-Wayne Major Airport at Romulus, which was 10 miles closer to Detroit than Willow Run.
In 1946 the University acquired Willow Run airport in Ypsilanti, Michigan from the federal government for $1.00, both with the responsibility for operating the airport and as well as using some of its buildings for a research center, the Willow Run Laboratories, administered as part of the Engineering Research Institute (ERI) of the University.
Willow Run's relative isolation encouraged new approaches to passenger transportation to and from airports; at Willow Run in 1946, Warren Avis founded Avis Airlines Rent a Car Systems, the first rental car operation at an airport.
Almost all of Detroit's scheduled airline flights used Willow Run until 1958, when the coming of the Jet Age drove traffic to the Romulus airfield, which had that year been renamed Detroit Metropolitan Wayne County Airport (the name it bears to this day), and offered carriers the promise of more efficient and modern operations, with a brand-new terminal designed for the new aircraft, a newly-expanded runway configuration and state-of-the-art approach controls that made it the first inland airport in the country certified for commercial jet operations.
