At the time the helicopter carrying Kobe Bryant crashed on Sunday, the weather conditions were so bad that both the Los Angeles Police Department and the Los Angeles County Sheriff’s Department had grounded their helicopters. “The weather situation did not meet our minimum standards for flying,” police department spokesman Josh Rubenstein said.

Humidity in the area reached 100 percent, indicating a fog dense enough to severely limit a pilot’s visibility.

CNN reported Monday that, according to a website that monitors air traffic control conversations, LiveATC.net, the pilot was not operating under the visual flight rules, VFR, that require good enough visibility to see terrain and position, but under special visual flight rules, SVFR, allowing them to remain in the air when others had decided not to fly.

In a press conference later Monday, the National Transportation Safety Board’s Jennifer Homendy told reporters that the pilot had to circle in the air for 12 minutes before obtaining approval to fly in controlled airspace.

She also said the helicopter crashed shortly after the pilot informed air traffic control that the aircraft would be climbing to avoid fog. When the pilot was asked what his plan was, Homendy said there was no response.

A radar record of the helicopter’s route, provided by FlightRadar24, showed it flying a constant northern course from where it took off, John Wayne Airport in Orange County, south of Los Angeles, until it reached Glendale, where it then appeared to circle in a holding pattern, before continuing northwest across the San Fernando Valley, following the route of Interstate 5, and then breaking away to the south.

A helicopter pilot familiar with the area told CNN on Sunday that there are often sudden changes in visibility on this route, from clear skies to heavy mists and fog. This pilot said that, when weather closes in, it is customary to use Pacific Coast Highway 101, the main coastal route from Los Angeles to Santa Barbara, as a navigational guide.

Before Highway 101 reaches the coast, it runs westward across the southern end of the San Fernando Valley. The FlightRadar24 tracking suggested that in the final minutes of the flight the pilot was heading for that highway, precisely where it follows a valley directly to the destination, Thousand Oaks. But, instead of following the line of the highway and the valley through the hills, the helicopter seemed to veer south, where it crashed in the hills near Calabasas.

But even if the weather was a plausible (at least partial) cause, it could have combined with other factors to prove fatal to the flight.

There is a question, for example, about whether the pilot would have been dependent on visual flight rules alone rather than in combination with a ground proximity warning system that is normally part of its instruments. Any one of a number of technical problems, from a systems failure to engine trouble, could have created a distraction.

The helicopter involved, a Sikorsky S-76, was nearly 30 years old, and investigators will be closely examining its maintenance record to see if there were any recent mechanical problems.

The Sikorsky S-76 is produced by a company with a storied history as a pioneer of helicopter technology and a record of attention to safety. According to a Los Angeles Times analysis of National Transportation Safety Board accident reports, between 2006 and 2016, the Sikorsky S-76 had the lowest rate of fatal accidents of all the helicopters in civilian use in the United States.

To those who never fly in helicopters—which statistically means most people—they may seem particularly prone to crashes. That is misleading. Civilian helicopter accidents have a distinct demographic of their own that makes them newsworthy.

There are basically three groups of people who most frequently fly by helicopter: The rich, powerful, and famous; sightseeing tourists; and those who fly for emergency services and law enforcement.

According to the Federal Aviation Administration, since 2006, the worldwide helicopter fleet has grown by 30 percent but the number of accidents has decreased by between 30 and 50 percent. Another body, the International Helicopter Safety Team, surveyed the record in 49 countries and found that between 2013 and 2017 fatal helicopter accidents fell by 17 percent.

The highest risk for helicopter crashes is for those used by emergency medical services. An analysis carried out of NTSB helicopter crash reports between 1983 and 2005 showed that of 182 accidents during that period, 39 percent were fatal. The deaths in those crashes included 45 percent of patients and 32 percent of crew-members. One reason given was the need to fly often at night and in all weathers.

Survivability concerns in a helicopter crash are compounded compared to those in traditional airplane travel. Many civilian helicopters are, where possible, routed over water to conform with noise regulations over populated areas. This means that the ability to get out of a ditched helicopter before it sinks is vital.

In 2018, five people died after a sightseeing helicopter crashed in New York’s East River. It had flotation devices that might have prevented it from sinking, but they reportedly failed to properly deploy. While the pilot was able to escape, the passengers drowned because they were still strapped in their safety harnesses.

Still, corporate titans continued to commute from East River helicopter pads to the Hamptons every weekend of the summer season with an insouciance suggesting that, for those with means, there was little fear of flying without wings.