FLAGSTAFF, Ariz. (AP) — The Federal Aviation Administration says the sightseeing helicopter that crashed at the Grand Canyon wasn't required to have a fuel system to prevent the aircraft from bursting into flames on impact.
Three Britons died and four others were injured in Saturday's crash at the canyon west of the national park.
Photos from the scene showed the helicopter in flames.
A witness has said he heard explosions and saw one survivor with extensive burns.
The FAA requires helicopters newly certified after 1994 to have a crash-resistant fuel system to prevent or lessen burn injuries.
But the regulations don't apply to newer versions of a helicopter designed before then.
The National Transportation Safety Board investigators are combing through the wreckage Tuesday and will determine if the helicopter had been retrofitted with the system.