Kobe Bryant's widow Vanessa filed a lawsuit on Monday against the operators of the helicopter that crashed on January 26, killing the NBA icon and eight others.

The suit was filed in Los Angeles Superior Court on the same day that Bryant, his 13-year-old daughter Gianna and the other seven crash victims were memorialized in a public ceremony at the Staples Center.

The lawsuit names Island Express Helicopters, Island Express Holding Corp. and the estate of the helicopter's pilot, Ara Zobayan, who was among the victims.

Gianna Bryant's basketball teammates Alyssa Altobelli and Payton Chester, Altobelli's parents John and Keri, Payton's mother Sarah and basketball coach Christina Mauser were also killed.

The National Transportation Safety Board is still investigating the exact cause of the crash, although preliminary findings showed no sign of mechanical failure.

Monday's lawsuit faults the company for allowing the helicopter to fly in "heavy fog and low clouds" that Sunday morning, conditions which prompted "law enforcement agencies and tour companies" to ground their helicopters. 

"On information and belief, Island Express Helicopters Federal Aviation Administration operating certificate limited its pilots to flying only under visual flight rules," the lawsuit says.

"The subject helicopter was not licensed or certified to be flown into instrument conditions. On information and belief, the pilot-in-command, Ara George Zobayan, was required to fly only in conditions that he could navigate visually.

"Ara George Zobayan attempted to maneuver the helicopter up and forward to clear the clouds, then entered a turn sending the helicopter into steep terrain at approximately 180 mph," according to the suit. "Witnesses on the ground reported seeing the helicopter flying through a layer of clouds and fog before the helicopter crashed."

The lawsuit notes that in 2015 Zobayan was cited by the FAA for violating the visual flight rules minimums by "flying into an airspace of reduced visibility from weather conditions."

Island Express did not immediately comment on the suit, which seeks unspecified general, economic and punitive damages.