Chicago Executive Airport:

A small plane making a cargo run had almost reached Wheeling's Chicago Executive Airport when it crashed in a forest preserve Tuesday afternoon, killing the two men aboard and setting off an investigation into the cause.

Officials said the Learjet 35A, owned by Royal Air Charter of Waterford, Mich., left suburban Detroit about 90 minutes before the crash and was scheduled to pick up cargo in Wheeling and ferry it to Atlanta. It had been cleared to land at Chicago Executive Airport when it went down about 1:30 p.m., officials said.

Debris was scattered in the woods of a Cook County forest preserve about a mile from the airport, and the fuselage was partially submerged in the Des Plaines River. The water was slick with fuel.

Officials found two bodies in the wreckage, but said they might not be able to recover them until Wednesday.

Authorities offered no initial theories about what caused the crash. The National Transportation Safety Board indicated its probe would focus on the plane.

"We will look at the systems, the structure, the engine," said senior safety investigator Pam Sullivan.

Robert Mark, a veteran commercial pilot who flew into Chicago Executive Airport shortly after the accident, believes the crash showed all the signs of a stall, the loss of lift that keeps a plane airborne.

"When they go in nose down, that's a classic stall spin. There's almost no other option," Mark said.

The stall could have occurred as the plane circled to make its final approach to the runway, experts said.

A circling approach was required Tuesday because winds were out of the west-northwest. The circling pattern is a more complicated maneuver than just coming in straight.

Authorities did not release the identities of the pilot and co-pilot, and officials at Royal Air declined to comment.

But spokesman J. David VanderVeen of the Oakland County International Airport, where the plane was based, said company officials told him the men were experienced with the Learjet.

Chicago Executive saw its last fatal crash in January 2006, when a twin-engine Cessna plunged into a construction company's storage yard as the plane approached the airport. The NTSB later concluded that pilot error was behind the crash that killed four Chicago-area executives.

According to NTSB records, Royal Air's last fatal crash happened on an overnight, three-leg flight in March 2004. A twin-engine plane had already ferried cargo from Rockford to Maryland when it crashed before dawn on its way to Maine. Investigators said the pilot lost control, but they couldn't figure out why.

Court and FAA records show that the 31-year-old company, with a fleet of 35 planes, has run afoul of safety rules. In 1999, the company agreed to pay a $250,000 fine for maintenance and record-keeping violations. Federal prosecutors complained the company didn't conduct scheduled inspections of fleet engines, propellers and wing flaps.

Patrick Doherty, who lives about 400 yards from the crash site, said 20 minutes before the plane came down, he had been walking his two dogs on that very spot. He said he was resting at home when he heard a noise that he thought came from his furnace.

Only later, when he heard the racket from a helicopter hovering above the site, did he realize something far more serious had happened -- and that he had been lucky to come home when he had.

"I was thinking, 'How weird is this? You go for a walk and get hit by a Learjet,' " he said. "It's kind of bizarre."