Jeremy Ead and Olivia Feldman filed a lawsuit Wednesday in Los Angeles County Superior Court, alleging that the park's neglect caused the ride to be "dangerous, defective, hazardous and unsafe," according to the suit.
A representative for Six Flags declined to comment.
The Ninja coaster partially derailed when it struck a tree that had fallen onto the tracks, according to the California Division of Occupational Safety and Health, which is investigating the accident.
Two riders were transported to hospitals with what park officials described as minor injuries. Firefighters helped evacuate 22 riders who were stranded in a disabled coaster car about 40 feet above the ground.
The park failed "to provide a safe and fit vehicle, so as to cause plaintiff to suffer injuries and damages," the lawsuit charges.
Ead told reporters after the accident that a tree branch hit him in the head as he rode the coaster, leaving him bleeding.
The lawsuit, filed by attorney Barry Novack, seeks money to cover legal costs, medical bills and lost earnings.
Novack recently filed a suit against