Petty Officer Nathaniel Parks said the plane went down shortly after 10 a.m. a few miles off the shore of Ludington, a resort town on Michigan's west coast. A passenger was rescued shortly after noon.
Federal Aviation Administration spokeswoman Elizabeth Isham Cory says the Cessna 206 left Alma Friday morning en route to Rochester, Minn. Alma is in central Michigan about 150 miles northwest of Detroit.
Parks says the crash was reported by a witness as well as a distress signal from the plane via satellite.
A map of the plane's flight path from flightaware.com suggests problems developed early in the flight. About one-third of the way into the flight, the westbound flight doubled back for a time over Lake Michigan and then turned straight north. It nearly reached the northern shore before going down.
This isn't the first time a medical flight has crashed in Lake Michigan. A Survival Flight plane carrying donor organs for a double lung transplant operation crashed in June 2007 into the lake near Milwaukee on its way to the University of Michigan Health System hospital in Ann Arbor. All six people on board the Cessna 550 Citation were killed.
