Photo: The Canadian Press

Coroner's officials worked to recover victims' remains Monday from the hillside outside Los Angeles where a helicopter carrying former NBA superstar Kobe Bryant and eight others crashed in a wreck that aviation experts said may have been caused by the pilot becoming disoriented in the fog.

While the cause of the tragedy is under investigation by the National Transportation Safety Board, some experts raised questions of whether the helicopter should have even been flying. The weather was so foggy that the Los Angeles Police Department and the county sheriff's department had grounded their own choppers.

Bryant's Sikorsky S-76 went down Sunday morning, killing the retired athlete along with his 13-year-old daughter Gianna and everyone else aboard and scattering debris over an area the size of a football field.

The pilot, identified as Ara Zobayan, had asked for and received special clearance to fly in heavy fog just minutes before the crash. Several aviation experts said it is not uncommon for helicopter pilots to be given such permission, though some thought it unusual that it would be granted in airspace as busy as that over Los Angeles.

But Kurt Deetz, who flew for Bryant dozens of times in the same chopper that went down, said permission is often granted in the area.

"It happened all the time in the winter months in LA," Deetz said. “You get fog.”

Air traffic controllers noted poor visibility around Burbank to the north and Van Nuys to the northwest. At one point, the controllers instructed the chopper to circle because of other planes in area before proceeding.

Randy Waldman, a helicopter flight instructor who teaches at the nearby Van Nuys airport, said its likely the pilot got disoriented in the fog and the helicopter went into a fatal dive.

“It’s a common thing that happens in airplanes and helicopters with people flying with poor visibility,” Waldman said. “If you’re flying visually, if you get caught in a situation where you can’t see out the windshield, the life expectancy of the pilot and the aircraft is maybe 10, 15 seconds, and it happens all the time, and it’s really a shame.”

“A lot of times somebody who’s doing it for a living is pressured to get their client to where they have to go,” Waldman said. “They take chances that maybe they shouldn’t take.”

Jerry Kidrick, a retired Army colonel who flew helicopters in Iraq and now teaches at Embry-Riddle Aeronautical University in Prescott, Arizona, said the helicopter's rapid climb and fast descent suggest the pilot was disoriented.

When that happens, he said, pilots must instantly switch from visual cues to flying the aircraft using only the machine’s instruments.

“It’s one of the most dangerous conditions you can be in,” Kidrick said. “Oftentimes, your body is telling you something different than what the instruments are telling you. You can feel like you’re leaning to the left or the right when you’re not. If the pilot isn’t trained well enough to believe the instruments, you get in a panic situation."