The 2010 helicopter crash that killed former Islander and billionaire businessman Tom Stewart and four others was most likely caused by Stewart’s young daughter, according to a recently released federal report.

The Valentine’s Day crash, which took place near Pheonix, Ariz., killed all on board, including Stewart, his daughter, wife and brother-in-law, as well as his pilot Rick Morton, also a former Islander.

An investigation completed this month by the National Transportation Security Board (NTSB) found that it is “highly likely” that Stewart’s 5-year-old daughter Sydney was riding in Stewart’s lap in the co-pilot’s seat and accidentally pushed down on the helicopter’s controls with her foot.

When either Stewart or Morton tried to correct the helicopter, the sudden movements caused one of the helicopter’s main blades to bend, strike the aircraft’s tail and break, according to the report. It is not known whether Stewart or Morton was flying at the time of the accident.

The helicopter, which was transporting the family from Stewart’s ranch in Flagstaff to his home in Scottsdale, crashed in a desert wash about 30 miles outside Phoenix and burst into flames, killing all five passengers instantly. The NTSB investigation into the crash was based on witness accounts, interviews, flight simulation, a post-accident examination of the aircraft and a biomechanical study.

The report also said that Stewart, who did not have a helicopter license, often took control of the cockpit duties and flew the aircraft, and that Morton, the pilot, did not maintain strong cockpit discipline when he allowed Stewart’s daughter to sit up front in his lap.

Stewart’s company and the lawyer for the pilot’s family, however, say they don’t agree with the NTSB findings. Gary C. Robb, an attorney who specializes in aviation accidents and represents Morton’s family, told the Associated Press this month that he believes the accident was caused by a faulty repair to one of the helicopter’s blades that resulted in the blade coming apart mid-flight. Robb filed a suit against the helicopter’s manufacturer as well as the mechanic that completed the repair.

“That’s their interpretation, and it does not comport with what our experienced investigators believe happened,” Robb told the AP.

Stewart was the chairman and CEO of Services Group of America, the nation’s largest food service distributor. He lived on Vashon at the 250-acre Misty Isle Farm until 2006, when he moved his company’s headquarters from West Seattle to Arizona.

On Vashon, Stewart was known as a generous and sometimes controversial figure who held large Republican gatherings at his estate, which was put on the market in 2007 for $125 million.

For years Stewart funded the annual Fourth of July fireworks display over Quartermaster Harbor. He also helped shape Vashon’s business scene, silently backing several Island establishments, and made significant contributions to the Vashon Park District and the Island’s equestrian community.