Pilot Ara Zobayan was climbing out of the clouds when the aircraft banked left and began a sudden descent that lasted nearly a minute.
"This is a pretty steep descent at high speed," said Jennifer Homendy of the National Transportation Safety Board. "We know that this was a high-energy impact crash."
The aircraft was intact when it hit the ground, but the impact of the crash spread debris over more than 500 feet. The last of the bodies and the wreckage were recovered from the Calabasas, California, hillside Tuesday, authorities said.
Autopsies confirmed the deaths of Bryant, Zobayan, John Altobelli and Sarah Chester, the medical examiner reported. The names of the five other victims have not been released, but they have been publicly identified as Bryant's 13-year-old daughter Gianna; Chester's 13-year-old daughter, Payton; Altobelli's wife, Keri, and daughter Alyssa; and Christina Mauser, a girls' basketball coach at a Southern California elementary school.
Determining what caused the crash will take months, but investigators might recommend that, to avoid future crashes, helicopters be equipped with a terrain awareness and warning system that would have sounded an alarm if the aircraft was in danger of crashing.
The agency made that recommendation after a similar helicopter, a Sikorsky S-76A carrying workers to an offshore drilling ship, crashed in the Gulf of Mexico near Galveston, Texas, killing all 10 people on board in 2004.
The NTSB concluded if a terrain awareness and warning system had been installed, pilots would have been warned in time to prevent hitting the water. The board recommended the Federal Aviation Administration require the warning systems on turbine-powered helicopters capable of carrying six or more passengers.
Ten years later, the FAA required such systems on air ambulances but not other helicopters. FAA officials questioned whether the technology would work on helicopters, which fly lower and could trigger too many false alarms that might detract from safety.
The NTSB said FAA's response was unacceptable but dropped the matter.
The helicopter flying Bryant did have a warning system using GPS, said pilot Kurt Deetz, who flew the longtime Lakers star dozens of times in the aircraft over a two-year period ending in 2017.
NTSB investigator Bill English said they are looking to document whether there was a GPS-based terrain avoidance system, but said it "doesn't look to be part of the scenario."
Zobayan, 50, was well-acquainted with the skies over Los Angeles and accustomed to flying Bryant and other celebrities. He spent thousands of hours ferrying passengers through one of the nation's busiest air spaces and training students how to fly a helicopter. Friends and colleagues described him as skilled, cool and collected.
Zobayan had flown the day before the crash on a route with the same departure and destination -- Orange County to Ventura County. But on Sunday, he had to divert because of heavy fog.
The decision to proceed in deteriorating visibility was questioned by some experts and fellow pilots.
Jerry Kidrick, a retired Army colonel who flew helicopters in Iraq and now teaches at Embry-Riddle Aeronautical University in Prescott, Arizona, said there can be pressure to fly VIPs despite poor conditions, a situation he experienced when flying military brass in bad weather.
"The perceived pressure is, 'Man, if I don't go, they're going to find somebody who will fly this thing,'" Kidrick said.
The chartered Sikorsky S-76B crashed into a cloud-shrouded hillside as Bryant was on his way to a youth basketball basketball tournament in which Gianna was playing.
NTSB investigators said Zobayan asked for and received permission from air traffic controllers to proceed in the fog. In his last radio transmission before the helicopter went down, he reported he was climbing to avoid a cloud layer.
Investigators have not faulted his decision to press on or explained why he chose to do so.
Deetz said he often flew Bryant to games at Staples Center, and never remembered Bryant or his assistants pressing him to fly in bad weather.
"There was never any pressure Kobe put on any pilot to get somewhere -- never, never," Deetz said. "I think he really understood professionalism. 'You do your job. I trust you.'"
Deetz said he flew with Zobayan a half-dozen times and that Zobayan was familiar with airspace and terrain around Los Angeles and knew "the back doors" -- alternative routes in case of trouble, such as changes in the weather.
Others who knew Zobayan praised him as unflappable and skilled at the controls.
"Helicopters are scary machines, but he really knew what he was doing," said Gary Johnson, vice president of airplane parts manufacturer Ace Clearwater Enterprises, who flew with Zobayan about 30 times in roughly eight years. "I wouldn't do it unless he was the pilot."
Zobayan was chief pilot for the craft's owner, Island Express Helicopters. He also was a flight instructor, had more than 8,000 hours of flight time and had flown Bryant and other celebrities, including Kylie Jenner, several times before.
Island Express has had three previous helicopter crashes since 1985, two of them fatal, according to the NTSB's accident database. All involved flights to or from the company's main destination of Santa Catalina Island, about 20 miles off the Southern California coast.
In 2008, three people were killed and three injured when an Island Express helicopter was destroyed as it came in for a landing on the island. Investigators said the chopper lost power, probably as a result of cracking in turbine blades inside the engine.
In 1985, an Island Express helicopter returning from the island collided with another copter near a landing pad in Los Angeles. One person died and 11 were injured.
Fatal helicopter accidents have fluctuated between 17 and 30 per year since 2013, according to a safety group that includes representatives of the helicopter industry and the FAA. The rate of accidents per hours flown has declined slightly over that time.
The FAA warns helicopter pilots that it is their job to decide whether to cancel a flight due to bad weather or other risks, and to have a backup plan in case weather worsens during the flight.
Inclement weather has been cited as a cause of other deadly celebrity helicopter crashes.
Grammy-winning blues guitarist Stevie Ray Vaughan was among five people killed in 1990 when their helicopter slammed into a hill in dense fog after leaving a concert in Wisconsin. Music promoter Bill Graham and two others, including the pilot, were killed when the pilot ignored warnings not to fly in rain and fog and flew into power lines outside San Francisco in 1991.
Bret Mosher, a commercial jet pilot in the Los Angeles area, said some plane owners pressure him to fly solo rather than with the added expense of another pilot.
"Typically these owners, they are successful people in business, they're type-A personalities. They are make-it-happen, get-it-done personalities," Mosher said. "A couple of them have said half-joking and half-serious -- well, probably more than half-serious -- 'Aren't you tough enough?' or 'Aren't you trained well enough?' or 'Aren't you good enough?'"
The Associated Press contributed to this report.
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