CHARLESTON, W.Va. (AP) — Inadequate inspections by an operator and a lack of oversight by the Federal Aviation Administration were partly to blame for the crash of a Vietnam-era tourist helicopter that killed six people in West Virginia two years ago, according to a final report released Tuesday.

The Bell UH-1B “Huey” helicopter showcased in action movies lost engine power and struck power lines during an attempted forced landing in June 2022 in Amherstdale, the National Transportation Safety Board said. The helicopter, which had taken off 15 minutes earlier from Logan County Airport, then smashed into a rock face and caught fire near a road.

Investigators say a component failure caused the loss of engine power. More comprehensive inspections by operator MARPAT Aviation, a Logan County flight school, likely would have uncovered fatigue cracks and other engine damage that led to the component’s failure, the NTSB said in a statement.

Someone who answered the phone at MARPAT Aviation on Tuesday said no one was available to comment before hanging up.

The NTSB said the FAA provided “basically no oversight” of MARPAT Aviation. At the time, the helicopter operated under a “special airworthiness certificate” in an experimental exhibition category. The certificate was issued in December 2014 by the FAA’s flight standards district office in Charleston. The NTSB noted that the FAA lacked guidance for inspectors to perform routine surveillance of operators with experimental airworthiness certificates.

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When the helicopter had a restricted-category certificate, last in effect in 2014, the operator followed more stringent inspection requirements, the NTSB said.

In addition, the Charleston district office was unaware that MARPAT Aviation was operating the helicopter at the 2022 event. No flight plan was required or filed for the local flight, the NTSB said.

Among six recommendations the NTSB made to the FAA include a review of airworthiness certificates issued to former military turbine-powered helicopters and requiring operators of experimental exhibition aircraft to disclose their events.

In a statement, the FAA said it “takes NTSB recommendations very seriously and will provide a response to the six new recommendations within an appropriate timeframe.”

The flight was the last one scheduled for the day during a multiday reunion for helicopter enthusiasts where visitors could sign up to ride or fly the historic Huey helicopter, described by organizers as one of the last of its kind still flying.

The helicopter was flown by the 114th Assault Helicopter Company, “The Knights of the Sky,” in Vinh Long, Vietnam, throughout much of the 1960s, according to the website for MARPAT Aviation. After the Huey returned to the U.S. in 1971, the website says, it was featured in movies such as “Die Hard, “The Rock” and “Under Siege 2: Dark Territory.”

During the reunion, people who made a donation could fly the helicopter with a “safety pilot” seated in the left front seat, according to the report. People could take a ride on the helicopter for a suggested donation.

The NTSB said the operator did not have a flight exemption that would have allowed the helicopter to be operated for compensation.

A private pilot, two “pilot rated” passengers and three others were killed in the crash. The 53-year-old pilot had flown the helicopter at the reunion event from 2020 to 2022, the NTSB said.

There were no known witnesses to the accident, according to the report.

Several wrongful death lawsuits were later filed on behalf of the helicopter’s passengers.