The National Transportation Safety Board said its investigation found no mechanical problems with the helicopter, a single-engine Bell UH-1H manufactured in 1967, and found that pilot Coleman Dodd was flying too low over mountainous terrain at night.
Besides Bennett, his wife Heather, Dodd, a co-pilot and wealthy businessman from Texas also were killed.
Bennett, who drew the wrath of former President Robert Mugabe, had won a devoted following in Zimbabwe for passionately advocating political change.
Andra Cobb, the businessman’s girlfriend and the co-pilot’s daughter, was the sole survivor of the crash. She recalled for authorities last year that the aircraft hit the ground with a loud bang before rolling, stopping upside down and bursting into flames on a grassy mesa top in northeast New Mexico.
She was able to free herself from her seat belt and escape the helicopter before it erupted in flames, she said.
Federal investigators previously reported that the fatally injured pilot said he’d flown into terrain near Raton, New Mexico. The NYSB report did not identify Dodd by name, but New Mexico authorities have previously said he was the lead pilot.
In a 911 call, Dodd told authorities immediately after the crash that three people were dead and there two other survivors, Andra Cobb and Bennett, who was suffering from a head wound. A search in the dark was slowed because of the rugged terrain and lack of access, officials said. First responders arrived on the scene nearly two hours after the crash, which occurred about 6 p.m., the NTSB report said.
As he was placed in a rescue helicopter, Dodd said the accident was his fault, according to a previous report. Dodd had thousands of hours of flying experience.
The NTSB report said a toxicology test showed Dodd had an antihistamine called diphenhydramine in his blood at the time of the crash. Investigators said a “therapeutic level” of the drug likely impaired him, but they could not say with certainty whether it was the reason he was unable to avoid crashing.
An autopsy report from New Mexico medical investigators last year also found a low concentration of fentanyl in Dodd’s system, but did not say whether he had taken it for health reasons.