But the National Transportation Safety Board said none of those factors could explain the fiery crash, which reduced the twin-engine Beech A100 King Air to a pile of twisted, blackened shards of metal in August 2008 near Canyonlands Field airport, 18 miles northwest of Moab.
It killed employees of a dermatology clinic who provided skin cancer treatment in rural areas.
Investigators determined only that the 41-year-old pilot, David White, failed to maintain ground clearance during takeoff for reasons apparently unrelated to any mechanical problem.
The plane wasn't steering toward its destination of Cedar City, about 200 miles to the west, and the pilot may have been trying to return to the airport or avoid restricted airspace over a defunct uranium mill, according to a NTSB report released Wednesday.
"The plane appeared to be operating well, and we don't know why the pilot" failed to keep it aloft, said Dane Leavitt, CEO of the Leavitt Group, a Cedar City insurance brokerage and owner of the plane, who employed White.
The NTSB determined the plane was nose-up when it crashed more than a mile from and 100 feet higher than a runway into a small hill.
The report found that White suffered from heart disease, with 90 percent blockage in one artery and 65 percent in another.
His wife said the 142-pound pilot was fit, played racquetball regularly and had no family history of heart disease.
Investigators couldn't determine if White had a heart attack because of the condition of his body, and Leavitt said he wouldn't speculate on that possibility.
The plane was pushing its weight limit in the hot, high desert of southern Utah, but the NTSB said that with both engines operating properly it should have had enough power to take off properly.
The report, however, provided confusing information on the plane's weight capacity and limits, and NTSB officials didn't immediately respond to requests late Wednesday for technical clarifications.
Leavitt said the plane wasn't overloaded but that he couldn't explain the NTSB findings.
"We appreciate the NTSB's efforts. They've clearly done a thorough job, and we're grateful for the conclusion that our plane was operating properly and it wasn't overweight. Our hearts go out to our friends who were on the plane and their families," he said.
The victims' families received a settlement from the Leavitt Group and its insurers about three months after the crash, he said.
Killed in the crash were pilot David White; Dr. Lansing Ellsworth, 50, his son Dallin, 23; Dr. David Goddard, 60, his daughter Cecilee, 31; Mandy Johnson; Marcie Tillery, 29; Valerie Imlay, 52; Keith Shumway, 29; and Camie Vigil, 25, all of Cedar City, Utah.