The Sikorsky S-76B helicopter carrying NBA superstar Kobe Bryant and eight others, including his 13-year-old daughter, was flying in tricky weather conditions before it crashed, investigators have found.

The aircraft departed at 9:06 am from John Wayne Airport in Orange County, on its way to Bryant’s Mamba Sports Academy in Newbury Park. It crashed into the mountains roughly 40 minutes later, killing all nine people on board and starting a small brush fire.

While it’s too early to say exactly what caused the wreck, dangerous conditions appear to be responsible.

According to investigators, the helicopter was flying through fog and low clouds at the time of the crash. Its pilot had reportedly obtained permission to fly under Special Visual Flight Rules (aka Special VFR) following a weather advisory that morning stating that, due to poor visibility, instrument flight rules would have to be implemented.

According to the Federal Aviation Administration’s Instrument Flying Handbook, instrument flight rules (IFR) are “Rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals.”

The investigation is being led by the National Transportation Safety Board (NTSB) and includes 18 experts. In addition to the weather conditions, they will take a close look at the pilot’s history and experience, as well as records pertaining to the maintenance of the helicopter and its owner and operator. It is not yet clear whether the helicopter contained a black box.

The aircraft was reportedly built in 1991.

“Aircraft must be inspected annually or every 100 flight hours, whichever comes first,” said Ian Gregor, public affairs manager for the Federal Aviation Administration’s Pacific division. “Additionally, certain parts must be replaced or overhauled at specific intervals. Maintenance records belong to the aircraft owner, who must make them available to the FAA for inspection upon request. The FAA looks at aircraft maintenance history as part of every accident investigation.”

Bryant was known to travel by helicopter. When he played for the Los Angeles Lakers he routinely used a helicopter to commute from his home in Orange County to the arena in downtown LA.

In 2017, the Los Angeles Times shared an anecdote that highlights Bryant’s devil-may-care attitude when it came to flying:

“Bryant and the pilot looked at each other and Bryant nodded subtly. Suddenly, to [Rob] Pelinka’s horror, the helicopter zoomed into military maneuvers designed to terrify the passengers, with the coup de grace coming near the end when the pilot shut off the engine in midair.”

Pelinka told the paper that while he “almost had a heart attack,” Bryant was “calm and collected.”