An attorney for the parents of a boy killed when an airliner slid off a runway and into their car urged witnesses and passengers Sunday to contact his office.

Lawyer Ronald Stearney Jr. said it was too early to say if Joshua Woods' parents would file a lawsuit, though autopsy results released Sunday determined the 6-year-old died from the impact of the plane hitting the car.

"It depends on how things unfold," Stearney said. "The first thing we have to do is bury the boy."

He asked people who saw the crash at Midway Airport on Thursday evening and those traveling aboard the Southwest Airlines plane to get in touch with him.

National Transportation Safety Board investigators spent Sunday examining controls in the cockpit of the plane, which had been moved from the city street to a hangar at the airport, NTSB spokesman Keith Holloway said.

After interviewing the pilots and crew on Saturday, the NTSB said the reverse thrusters on the jet's engines, which should have slowed the aircraft, appeared not to have activated immediately when the pilots tried to deploy them.

The Boeing 737, with 98 passengers, landed in a snowstorm Thursday and slid off the end of a 6,500-foot runway, through the airport fence and into traffic. It hit two cars, killing Joshua and injuring 10 other people.

Joshua's younger brothers, ages 4 and 1, suffered cuts and bruises. His mother, Lisa Woods, was briefly hospitalized. His father, Leroy Woods, left a hospital Saturday after treatment for fractures in his nose, face and back of his head, Stearney said.

Joshua's parents wanted to visit the crash site Saturday, but as they drove closer, the sound of jetliners triggered painful memories from the accident, and the couple from northwest Indiana decided to leave.

"We got near the airport but not actually near the crash site, because they had to look away," Stearney said.

Chicago Department of Aviation spokeswoman Wendy Abrams said the runway involved in Thursday's crash remained closed Sunday while workers repaired damaged navigation gear on the airfield.