The Biden administration is fighting to keep mask requirements in place on airplanes and other forms of public transportation, filing in court Tuesday to overturn a U.S. District Court judge’s April ruling that found the CDC’s mask mandate unlawful.

Judge Kathryn Kimball Mizelle of Florida in April said that the U.S. Centers for Disease Control and Prevention exceeded its statutory authority by imposing a mask mandate on airplanes, buses, trains, and other forms of public transportation and transportation hubs. She ordered the Biden administration to stop enforcing the mask requirements, and while the administration complied, the Department of Justice pledged to appeal the ruling.