United Airlines, Inc. has filed suit in federal court seeking a declaration that a 2020 state law mandating paid sick leave does not apply to its employees in Colorado.

The lawsuit, filed on Jan. 13, claims the Airline Deregulation Act of 1978 prohibits states from enacting regulations related to the “service of an air carrier.” Therefore, the law, as well as other federal provisions, allegedly preempts the requirements of the Colorado Healthy Families and Workplaces Act.

“That federal scheme is the exclusive source of sick leave for airline employees, and so United is not and should not be subject to the HFWA,” wrote attorneys for the company.

Colorado lawmakers enacted the HFWA in 2020 to provide up to 48 hours of annual, paid sick leave and 80 hours for reasons related to COVID-19 or other public health emergencies.

United alleges its collective bargaining agreements with pilots, flight attendants and ground crew contain sick leave policies similar to Southwest Airlines, which Colorado has deemed to violate the HFWA. Southwest filed a similar lawsuit in May of last year, and the government has moved to dismiss it on a variety of legal doctrines, arguing state courts should resolve the dispute there.

A federal judge has not yet ruled on the motion to dismiss the Southwest litigation.

The case is United Airlines, Inc. v. Moss.