Fire personnel and investigators at the scene of a Dec. 5, 2021, Piper PA-31-350 Navajo Chieftain airplane crash in the parking lot of the Airport Chevrolet GMC off Biddle Road in Medford.

A Nevada private pilot’s inability to see where he was going after takeoff from the Medford airport in 2021 caused the fiery crash that killed him and a passenger onboard, according to the final National Transportation Safety Board report on the accident.

The pilot, Donald Harbert Sefton, 69, of Fallon, Nevada, was qualified to fly and had received recurrent training a month before he departed the airport with Valerie Jean Serpa, 67, of Fallon on Dec. 5, 2021, according to the NTSB report issued Thursday.

But his “failure to maintain aircraft control during the initial climb into clouds due to spatial disorientation” led to the crash, which occurred around 4:52 p.m. in an Airport Chevrolet GMC parking lot off Biddle Road.

The dealership was closed at the time, and no one on the ground was killed or injured, according to news reports.

The reasons why Sefton experienced spacial disorientation while flying his Piper PA-31-350 Navajo Chieftain airplane, carrying 128 gallons of fuel, “could not definitely (be) determined,” the report said.

Sefton left the anti-collision lights on while in the clouds, which may have caused him to experience “flicker vertigo” — an imbalance in brain-cell activity caused by exposure to the flashing of a relatively bright light — according to the report. The report cited a portion of the airplane’s handbook, which states that such lights should not be used in cloudy weather for this reason.

Sefton’s airplane showed no signs of mechanical malfunctions before takeoff, according to the report.

The NTSB’s final report follows a preliminary report the agency issued Jan. 10, 2022. While both reports contain facts gathered during investigations, the final report provides an analysis that helps determine the probable cause of the accident, wrote Sarah Taylor Sulick, a public affairs specialist for the NTSB, in an email Friday.

The crash occurred almost two weeks after Sefton and Serpa flew into Medford from Fallon and noticed the plane was leaking a large amount of fuel from the right wing root. Repairs were made before their fatal flight, the report said.

Sefton, who had driven back to Nevada during repairs, intended to fly his plane home with Serpa on Dec. 5. They arrived at the airport in Medford around 4 p.m., the report stated.

Sefton was set to take off from runway 14 and issued a departure plan. Air traffic control informed him of the low-lying clouds.

After the airplane departed, Sefton asked the controller, “will you be calling my turn for the (departure procedure)?” The controller replied that he would not be calling his turn and that Sefton should fly the departure as published, according to the report. Sefton acknowledged the communication, but that was his last transmission.

Sefton was the head of a business he started in Fallon called System Consultants. The company has contracts with Nevada and Utah for processing the big game drawings, according to its website.

Serpa was director of the Oats Park Art Center and the Churchill Arts Council in Fallon, according to a Reno News and Review article.