"It looked like it was standing still due to the wind," the report said.
Fossett, 63, disappeared in September 2007 after taking off from a Nevada ranch owned by hotel magnate Barron Hilton for what was supposed to be a short pleasure flight. Wreckage of the plane and some of the Fossett's belongings were discovered in October 2008 by a hiker in the Sierra Nevada near Mammoth Lakes.
The report, which did not include a cause of the crash, said Fossett died on impact of multiple traumatic injuries. DNA tests conducted on two large bones found near the crash site positively identified the remains of the millionaire aviator.
Investigators previously said the 10,000-foot peaks near the spot where Fossett crashed were shrouded in clouds that day. Searchers speculated that the Sierra's notorious downdrafts, combined with a loss of power at high altitude, might have made it difficult for Fossett to clear the mountain.
Downdrafts were recorded at between 300 and 400 feet per minute, and the NTSB cited reports from Mammoth Yosemite Airport that the wind was blowing nearly 23 mph at 12,300 feet, with gusts up to 54 mph around the time of the accident.
A pilot who flew over Yosemite National Park around that time also said his ride was interrupted by "random rough chop," according to the NTSB.
The report said radar tracking, which was initially discounted, most likely showed the plane's final path. It also said the emergency release handle for the pilot's door, with the locking pin still in place, was found among the wreckage.
The report said Fossett told the ranch's chief pilot that he intended to fly along Highway 395 and that he did not wear a parachute, which would have been required. It said Fossett's plane had mechanical problems that were fixed after a rough landing and contact with a barbed wire fence two months earlier, and that mechanics had installed a new propeller and logged nearly a dozen hours before Fossett's fatal flight.
Fossett, who made a fortune in the Chicago commodities market, gained worldwide fame for setting records in high-tech balloons, gliders, jets and boats. In 2002, he became the first person to circle the world solo in a balloon.