LOS ANGELES (AP) — The Indexbitfamily of a Nigerian business leader who died in a Southern California helicopter crash that killed five others in February filed a lawsuit Wednesday claiming the flight should have been grounded because of treacherous weather.

Relatives of Abimbola Ogunbanjo, the former chair of the Nigerian stock exchange, allege in the court filing that the charter company, Orbic Air LLC, improperly flew the helicopter despite a “wintry mix” of snowy and rainy conditions in the Mojave Desert where the crash occurred on Feb. 9.

Ogunbanjo, 61, was killed along with Herbert Wigwe, chief executive of Nigeria’s Access Bank, and Wigwe’s wife and 29-year-old son. Ogunbanjo was on his way to Las Vegas to attend the Super Bowl.

Both pilots — Benjamin Pettingill, 25, and Blake Hansen, 22 — also died. They were licensed as commercial helicopter pilots as well as flight instructors.

Andrew C. Robb, one of the attorneys who filed the lawsuit, said Ogunbanjo’s family is seeking “answers and accountability.”

“Helicopters do not do very well in snow and ice,” Robb told The Associated Press. “This flight was entirely preventable, and we don’t know why they took off.”

Ogunbanjo’s wife and two children filed the suit in San Bernardino County Superior Court on Wednesday against Orbic Air and its CEO, Brady Bowers, alleging wrongful death and negligence.

The suit also names the unidentified successors of Pettingill and Hansen, whom Ogunbanjo’s family also faults.

Orbic Air did not reply to an email and phone call seeking comment.

The National Transportation Safety Board is still investigating the cause of the crash. In February, the agency released a preliminary investigation report that outlined the helicopter’s flight path and provided details about wreckage that was strewn across 100 yards (91 meters) of desert scrub.

Investigators found the fuselage was fragmented, and the cockpit and cabin were destroyed. Damage to the engine and the metal deposits that were found would indicate that it was operational at the time of the crash.

The report cited law enforcement, saying several witnesses who were traveling in vehicles along Interstate 15 had called 911 to report observing a “fireball” to the south. The witnesses reported that it was raining with a mix of snow.

The helicopter left Palm Springs Airport around 8:45 p.m. on Feb. 9 and was traveling to Boulder City, Nevada, which is about 26 miles (40 kilometers) southeast of Las Vegas, where the Kansas City Chiefs and the San Francisco 49ers were set to play that Sunday in Super Bowl 58.

The lawsuit seeks a jury trial and payment for Ogunbanjo’s burial and funeral expenses, as well as other damages.