Fred Byrne of Big Rapids has been missing since Feb. 12, when he dropped off his son at Hope College in Holland and visited his mother.
Police in Big Rapids said a search took place Tuesday by helicopter. More efforts are planned by police in Missouri to find Byrne, 49, or uncover leads.
Byrne's Chevy Malibu was found Feb. 14 parked along a forest service road near Van Buren, Mo., which is about 160 miles southwest of St. Louis and about 560 miles from where he was last seen. Big Rapids police said Byrne's wallet and keys were in the car.