(Bloomberg) -- Southwest Airlines Co. pilots asked a court to temporarily block the company from carrying out federally mandated coronavirus vaccinations until an existing lawsuit over alleged U.S. labor law violations is resolved. 

The Southwest Airlines Pilots Association's filing Friday also asked for an immediate hearing on the request before a federal court in Dallas, claiming the carrier has continued to take unilateral actions that violate terms of the Railway Labor Act, which governs airline-union relations. Those steps include the Covid-19 vaccination requirement. 

"The new vaccine mandate unlawfully imposes new conditions of employment and the new policy threatens termination of any pilot not fully vaccinated by December 8, 2021," the legal filing said. "Southwest Airlines' additional new and unilateral modification of the parties' collective bargaining agreement is in clear violation of the RLA."

Southwest set the deadline on Oct. 4 under a federal vaccination mandate for employees of companies holding contracts with the U.S. government. Workers can seek medical or religious exemptions. The union represents 9,000 Southwest pilots.