On April 18, 2022, a federal judge struck down the mask mandate imposed on all travelers on U.S. public transportation by the Centers for Disease Control (CDC). U.S. District Judge Kathryn Kimball Mizelle ruled that the mandate was improper on procedural grounds. Neither the TSA nor the CDC will enforce the mask mandate for the time being, though it is not yet clear whether the court ruling will be appealed. The CDC continues to recommend masks on public transportation, and transportation systems and companies may establish their own rules regarding the use of masks.