In a sign that clouds, fog and limited visibility were of particular interest to investigators, NTSB board member Jennifer Homendy appealed to the public to come forward with any photographs that might help document local weather conditions at the time of the crash.
The NTSB offered no update on the search for victims but said investigators were expected to be on the scene for as many as five days.
The dense fog, and its role in the crash, came under scrutiny on Monday as fans, friends and relatives of the retired NBA great confronted the reality that the charismatic 41-year-old and his 13-year-old daughter, Gianna, were among those on board who died.
Bryant, who won five NBA championships in his 20 years with the Los Angeles Lakers, was known since his playing days to travel frequently by helicopter to avoid the Los Angeles area’s glacial traffic.
The National Basketball Association cancelled a game scheduled for Staples Centre on Tuesday between the Lakers and their crosstown rivals, the Clippers.
In addition to the Bryants, the crash devastated three other families linked to the Mamba Sports Academy: a husband and wife with their 13-year-old daughter; a mother and her 13-year-old daughter; and a basketball coach who was also a mother. They had been on their way to a basketball tournament.
The ninth victim was the pilot, Ara Zobayan, an experienced former flight instructor who was instrument-rated, or qualified to fly in fog, according to multiple US media accounts.
Witnesses recounted thick fog over the foothills where the helicopter went down. The fog was so bad that both the Los Angeles Police Department and Los Angeles County Sheriff’s Department grounded their helicopter fleets, the Los Angeles Times reported, citing officials.
Air traffic controllers gave the pilot “Special Visual Flight Rules,” or clearance to fly in less than optimal weather around the Burbank airport.
A Federal Aviation Administration (FAA) official noted a pilot “does not get a general, or blanket, clearance from the FAA to fly in these conditions. A pilot is responsible for determining whether it is safe to fly in current and expected conditions.”
Moreover, the pilot apparently requested “flight following,” or constant tracking from controllers, but was informed he was flying too low to be picked up by air traffic control radar. It is unclear if the pilot heard the comment as it came near the end of the doomed flight.
The radio traffic audio indicates the pilot tried to remain below clouds in order to remain in visual contact with the ground and avoid flying on instruments, said Gary Robb, an aviation lawyer and author of the book “Helicopter Crash Litigation.”
Robb said it was “certainly possible” that the pilot was “flying so low to get under the cloud cover that he clipped the top of that mountain that extended into the clouds.”
The pilot, in his transmissions, “was calm and controlled the whole time,” Robb said, calling the communications “extremely normal and routine”.