There is a huge one missing in northern Michigan. The site is used for winter testing by several auto companies. They have a website here: https://www.smithers

There is a huge one missing in northern Michigan. The site is used for winter testing by several auto companies. They have a website here: https://www.smithers.com/industries/transportation/automotive/winter-proving-grounds https://www.smithers.com/industries/transportation/automotiv... It was a large airport with 3 runways in a triangle configuration. Last time I was there I thought it was owned by Continental.