ORLANDO, Fla. (AP) _ The family of Payne Stewart is suing the owner and operator of the Learjet he was flying in when he died in a bizarre crash in South Dakota a year ago.

The lawsuit was filed in Orange County Circuit Court on Wednesday, a year to the day after he died, by Tracey Stewart and her children. It seeks an unspecified amount of damages and accuses Sunjet Aviation Inc. and Jet Shares One Inc. of negligence.

Lawsuits also were filed by the families of three others who died in the crash: Stewart's sport agents, Van Ardan and Robert Fraley, and golf course designer Bruce Borland.

The families hope the lawsuit clears up what really happened during the flight. They recognize that the results of the FBI investigation likely won't be made available to them, said Gerard Lear, their Washington-based attorney.

``What we're interested in primarily is obtaining a full history of the specific aircraft as well as any history of previous pressurization problems for that Learjet,'' Lear said.

The Learjet's cabin pressure system wasn't properly inspected, maintained or repaired, according to the lawsuit. In addition, the oxygen supply system and a valve in the engine weren't properly maintained and the plane's crew failed to take proper corrective measures in the emergency, according to the complaint.

``Defendants knew or should have known from the maintenance history of the aircraft that it was unairworthy and unsafe by reason of a dangerously defective cabin pressure system,'' the 11-page lawsuit said.

Mark Dumbroff, a Washington-based attorney for Sunjet, wouldn't comment until he sees the lawsuits. Sunjet, the Sanford-based company that operated the airplane, was dissolved earlier this year, and any damages will be pursued from the company's insurance company.

A woman who answered the phone at Jet Shares One Inc.'s registered agent, Delaware Registry Ltd. in Wilmington, Del., said she couldn't give out information on the company.

Maintenance logs released by the National Transportation Safety Board last month show that the Learjet had previous problems with its cabin pressure system. The logs also showed that a valve had to be replaced following inflight loss of cabin pressure on June 28, 1986.

The plane Stewart was on departed Orlando on Oct. 25, 1999, for Dallas. Radio contact was lost with the plane as it passed north of Gainesville. The flight continued on autopilot until it ran out of gas and crashed near Aberdeen, S.D.

There has been speculation that the cabin pressure system failed, causing the crew and passengers to pass out from loss of oxygen. The crash destroyed or damaged several parts of the oxygen and pressure systems. Some remain missing as the crash continues to be investigated.

PGA players at the National Car Rental Classic at Disney outside Orlando said Wednesday that the anniversary of Stewart's death was a painful reminder of what was lost.

``Completely healed? I don't know. I don't know if you ever really do,'' Tiger Woods said. ``Payne was such a fixture out there and a part of all our lives, and we accept the fact that he has gone to a better place. But the hard part is that he is missing in our lives.''