A helicopter appears to have crashed into a slackline strung across part of a remote Arizona canyon for an extreme tightrope-style activity, killing all four passengers.
The slackline was “more than one kilometer long,” according to the Pinal County Sheriff’s Office in Arizona, which added that a witness reported “seeing the helicopter strike a portion of the line before falling to the bottom of the canyon”.
The slackliners had filed an official aviation safety notice, known as a Notam, leading to questions about whether the pilot had seen the alert.
The cause has yet to be conclusively determined and investigators are currently probing the incident. An official report is due in 30 days.
A slackline is a long piece of strong fabric stretched above the ground. It holds less tension than a tightrope, allowing athletes to bounce and sway as they move across it. It can be strung low to the ground, or high in the air for an activity known as highlining.
“Preliminary evidence indicates a recreational slackline more than one kilometer long had been strung across the mountain range,” near Telegraph Canyon, east of Phoenix, said a sheriff’s statement released 2 January, the day of the crash.
“An eyewitness who called 911 reported seeing the helicopter strike a portion of the line before falling to the bottom of the canyon.”
The investigation is being led by the National Transportation Safety Board (NTSB) and the Federal Aviation Administration (FAA).
On Monday, officials confirmed the identities of the victims as family members from Oregon.
Pilot David McCarty, 59, was killed, along with his three nieces Rachel McCarty, 23, Faith McCarty, 21, and Katelyn Heideman, 21.
Investigators have taken the wreckage of the helicopter to a “secure facility for further examination,” NTSB spokesman Keith Holloway told the BBC in an email on Tuesday.
No one was on the slackline when the helicopter went down, he added.
Holloway added the NTSB has led “numerous investigations where aircrafts have impacted wires”, which can be very difficult for pilots to see, and that the agency has not yet concluded whether a slackline caused the crash.
It is unclear whether slacklines have ever caused a previous aviation accident.
The International Slackline Association released a statement saying it was “heartbroken” over the incident, and that the slackliners involved had taken proper safety measures, including attaching “aviation markers” to the line for increased visibility.
“The FAA had been informed of the highline and a Notam (Notice to Air Missions) had been issued before the collision,” it said.
A Notam is an air safety tool that alerts pilots about potential hazards along their routes, including flocks of birds or lawnmowers near runways. Pilots must check the system prior to take-off.
Aviation safety experts have criticised the Notam system as clunky and outdated.
Pilots must manually search through lists of notices, some of which may be unrelated to their planned flight, Tim Kiefer, professor of air traffic management at Embry-Riddle Aeronautical University, told CBS 5 in Phoenix.
“Some of them will be pertinent, some of them will not be pertinent. Some of them will have already happened, some of them will happen. And it’s up to the pilot or air traffic controller to go through these and find the ones that are pertinent to them,” Kiefer said.
In September, the Department of Transportation said the “legacy and aging” Notam system would be “fully” replaced by February 2026.
By BBC News
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