A federal judge in Texas on Monday ruled that United Airlines‘ employee vaccine policy can proceed.

The Chicago-based airline has one of the strictest employee vaccine policies in the country. In September, it said that staff who receive medical or religious exemptions would be placed on unpaid leave.

Six employees filed suit to block the policy in September.

U.S. District Judge Mark Pittman wrote in his ruling: “it is not for the Court to decide if United’s vaccine mandate is bad policy. Rather, it is the Court’s role to determine if Plaintiffs carried their burden to obtain a preliminary injunction.”

United said Monday that the roughly 2,000 employees who were granted religious or medical exemptions to its policy could apply for non-customer facing roles and that those who do not apply will be put on leave.

“We are working to identify non-customer facing roles where accommodated employees can apply and continue working until it is safe for them to their return to their current positions,” it said.

United has said that more than 96% of its 67,000-person U.S. workforce is vaccinated.