An Iowa marketing company had chartered the flight to take its co-founder and three employees on a business trip from Ankeny, Iowa, to South Bend, in northern Indiana.
Crash investigators had not determined the cause of Monday night's accident, but the plane began its return flight in poor weather, with limited visibility and fog.
"It was not a good night to fly," Deputy Coroner John Sullivan said.
The Cessna 303 crashed about 10 miles southwest of South Bend, shortly after departing from South Bend Regional Airport, according to the Federal Aviation Administration.
After takeoff, the pilot issued a distress call because of engine problems, said Brian Jones, a partner in Des Moines-based Two Rivers Marketing.
Investigators said the aircraft spiraled to the ground, killing the pilot and four passengers.
Debris and human remains were scattered over an area the size of a football field, Sullivan said. Crews used a crane to pull wreckage from the field, where it was embedded several feet into the earth.
Pam Sullivan of the National Transportation Safety Board said an autopsy was planned to determine whether the pilot had any medical condition that might have caused him to lose control of the plane.
The aircraft apparently reached 5,700 feet and then tumbled almost vertically to 1,200 feet, where it vanished from radar, she said.
Resident Cathy Olson said the plane sounded like it was in trouble when it flew overhead. "All of a sudden, we heard a big bang," she said.
Jones told the Des Moines Register that the fatal flight marked only the second time the company had chartered a plane. Employees had previously traveled by commercial airlines, he said.
The newspaper published a report on the businesses' recent expansion in its Tuesday edition; the story was written before the crash.
Two Rivers Marketing identified the victims, all from Iowa, as co-founder Tom Dunphy, 41, Eric Jacobs, 31, Josh Trainor, 23, and Leslie O'Bannon, 27. Also killed was pilot John M. Trewet, 45, officials said.