FLAGSTAFF, Ariz. (AP) — The pilot of a helicopter that crashed in the Grand Canyon in 2018, killing five British tourists, told investigators that he wasn't able to control the aircraft after a “violent gust of wind” sent it spinning, according to a new report.

The National Transportation Safety Board released its final report Thursday that said tailwinds, potential downdrafts and turbulence were the probable cause of the loss of control and tail-rotor effectiveness. The investigation found no evidence of mechanical problems with the helicopter.

The report did not include any safety recommendations.

The Airbus EC130 B4 crashed just before sunset in February 2018 in a section of the Grand Canyon where air tours aren't as highly regulated as in the national park.

The pilot, Scott Booth, was attempting to land next to the Colorado River on the Hualapai reservation when the gust hit.

“It just took the aircraft from me,” he told investigators in an interview months after the crash. “It just spun it, and I couldn’t fly it. It just took it so quickly.”

Witnesses saw the helicopter make at least two 360-degree turns before hitting the ground and bursting into flames.

Three of the British tourists on board were pronounced dead at the scene: veterinary receptionist Becky Dobson, 27; her boyfriend and car salesman Stuart Hill, 30; and Hill’s brother, 32-year-old lawyer Jason Hill.

Two others in their group — 31-year-old Jonathan Udall and 29-year-old Ellie Milward Udall — later died from burn injuries.

Booth fractured his lower left leg, and passenger Jennifer Barham had a spinal fracture. They also suffered severe burns but survived.

An attorney for Jonathan Udall, Gary C. Robb, called the NTSB investigation thorough and well-researched.

“The Udall family from the beginning has wanted to find out what happened so this can prevent other helicopter victims from literally being burned alive,” he said.

The investigation by the National Transportation Safety Board revealed a chaotic attempt to render aid. Witnesses who included other pilots, passengers and a wedding party in the canyon saw smoke and heard screams after the helicopter crashed. Some people ran toward the flames to help, against the pilots' advice to stay close to picnic tables.

Witnesses saw two women emerge from the flaming wreckage, dazed, burned and bleeding and in shock. They were screaming for their loved ones, pilots said.

The British tourists boarded the helicopter earlier that day in Boulder City near Las Vegas as part of a trip to celebrate Stuart Hill's birthday and the Udalls as newlyweds.

Booth had worked for the air tour company Papillon since June 2013, most recently part-time. He had flown passengers into the Grand Canyon and landed in the gorge nearly 600 times. Most days, the weather was calm and the flights routine, he said.

As Booth approached the canyon, he took note that other parked helicopters were pointing different directions and saw a windsock “waving like a waffle." He slowed down to land and was hit hard by the wind, maneuvering to try to gain control, he said.

Next thing he knew, he was up on a ledge, and his pants were on fire. Another pilot used a tourniquet on Booth's leg. Others were covering him with blankets and jackets, he said.

Witnesses tried to use a satellite phone, but the battery was dead. They attempted to draw power from a helicopter but had no service. A box containing medical supplies had to be smashed open because no one knew the combination to the lock, according to the NTSB report.

Pilots began ferrying emergency responders who reached the site about 45 minutes later, the report said. Victims weren't transported to hospitals for six hours because of the remoteness of the area and communications issues, the NTSB said.

Authorities summoned rescue crews and reached out to Nellis Air Force Base to see if anyone who was qualified in night vision could help.

Eventually, fatigue set in for helicopter pilots, and they stopped flying passengers and emergency personnel back up to the rim. Several passengers and members of a volunteer rope team slept in helicopters in the canyon or on picnic tables.

The three pilots who landed before Booth said they, too, had to contend with wind that became progressively stronger. The NTSB said photographs of the windsock at the landing site indicated gusts of at least 15 knots, or 17 mph (27 kph). Investigators said pilots estimated even stronger gusts.

“I went from having airspeed to not having any at all,” one of the pilots, John Davis, told investigators. “I don’t know how I kept it straight. I kept thinking about that. Had I said something on the radio, maybe he (Booth) would not have followed that direction.”

Papillon's guidelines said helicopter operations could be suspended with gusts of 20 knots or 23 mph (37 kph) or wind speeds that were higher and more steady.

Pilots flying that day anticipated wind. But the NTSB said it's unlikely they were alerted to weather advisories about turbulence and stronger winds that were issued after their morning briefing. Booth said he didn't check the weather after that briefing.

Investigators also noted that the helicopter lacked a crash-resistant fuel system. The helicopters in Papillon's fleet weren't required to have them, but the company has since retrofitted the aircraft with fuel tanks that expand and seal upon impact instead of rupturing.

After the crash, Papillon also placed new satellite phones with better coverage, trauma kits and a collapsible metal stretcher in unlocked metal containers in the canyon for emergencies. It also added a wind sock near the accident site. The helicopter manufacturer, Airbus, updated its safety information for pilots.

The family of Jonathan Udall sued the helicopter company and the aircraft manufacturer, accusing them of failing to equip the helicopter with the crash-resistant system. That case is ongoing.

The NTSB said its requests through Barham’s family to interview her were declined.