There are now eight plaintiffs in the lawsuit alleging "wilful and wanton misconduct" against Mi Joo Tour and Travel, whose bus smashed through a highway barrier and tumbled down a snow-covered cliff on Dec. 30.
The civil claim has added the company's president as a defendant, alleging Edward Kang established management policies based on cost and profit rather than the safety of passengers.
Added to the lawsuit are man who broke both his legs, his wife who died in the crash, and two Korean brothers who were studying English in Washington state.
A woman who sustained multiple fractures and her husband, who was not a passenger but is claiming for loss as a result of his wife's injuries have also joined the suit.
A lawyer for the bus company has previously said black ice led to the crash rather than driver fatigue, even as a U.S. government audit found the man had been on the road for 92 hours in the eight days prior.