The 26 workers drive the company's rental cars to and from the airport for cleaning and refueling. They are among 34 Hertz employees suspended Sept. 30 for failing to clock out before breaks.
Eight of the 34 signed the clock-out agreement and have returned to their jobs, company spokesman Rich Broome told The Associated Press Friday in an email. Termination letters have been sent to the rest.
The company made it clear the suspended workers needed to agree to the clock-out conditions by the end of the day Thursday if they wanted to be reinstated, Broome told The Seattle Times.
The firings were first reported by KOMO-TV.
Broome told the AP earlier this month "It's not about prayer, it's not about religion; it's about reasonable requirements."
Observant Muslims pray several times a day.
Hertz said the suspended workers were violating provisions of a collective bargaining agreement and a settlement with the Equal Employment Opportunity Commission reached two years ago.
Teamsters Local 117, which represents the workers, said the two sides were unable to negotiate an agreement that would have allowed the workers to return to their pre-suspension status, under which they wouldn't have to clock out to pray.
Union spokesman Paul Zilly said the workers were given an ultimatum to sign the clock-out document.
If Hertz felt some employees were abusing the break policies, it should have dealt with them individually, Zilly said.
The union said the break clock-out requirement is not in the contract and Hertz had agreed during negotiations last year that it would not require it.
The union has filed an unfair labor practices complaint with the National Labor Relations Board. The union also said it is filing religious discrimination charges with the EEOC.
The union represents nearly 80 Hertz drivers who earn between $9.15 and $9.95 an hour. About 70 percent are Muslims.