The Biden administration appealed a federal court ruling that struck down the mask requirement for passengers on planes, trains, buses and other public transportation.

The decision came two days after a federal judge in Florida struck down the mask mandate, setting off a rush among airlines, some public transit systems and even ride hailing services to abandon mask requirements. Some pilots announced the change midflight, prompting celebration, but also anxiety among passengers.

The C.D.C. is trying to keep the mandate intact while also trying to keep its public health powers. If the ruling striking down the mandate is upheld, it could permanently weaken the agency's authority.

If the Biden administration wins the case, there will be backlash from Americans who felt liberated by the lifting of the mask requirement.

The status of the mask mandate, which cannot be reinstated unless the administration wins a stay of the Federal District Court's order, was not changed by the legal moves. Legal experts said that if the administration asked for a stay, the court could make a decision within a few days.

As the BA.2 subvariant threatens to unleash another deadly wave, the Justice Department's appeal comes as cases, though not hospitalizations and deaths, are rising in a majority of states.

The mandate was put in place shortly after President Biden took office and was set to expire on April 18. The C.D.C. extended the rule until May 3 to give public health experts more time to assess whether it should be continued.

The case could end up before the Supreme Court because the 11th Circuit has a conservative bent.

The future ability of our nation's public health agencies to protect the American public is at stake as a result of this clash between public health and a conservative judiciary.

The White House press secretary said in an interview with Chris Wallace that the appeal was important to ensure the authority and ability of the C.D.C.

The mandate had outlived its usefulness, according to an official with the U.S. Travel Association.

With low hospitalization rates and multiple effective health tools now widely available, she said, required masking on public transportation is simply out of step with the current public health landscape.

The transportation mandate was voided on several grounds, including that the agency had exceeded its legal authority under the Public Health Service Act of 1944.

The Department of Justice decided to appeal the ruling if the C.D.C. decided that the mandate was still necessary. The C.D.C. made its position clear.

C.D.C. believes that it has legal authority to protect public health.

The statement said that when people wear a well-fitting mask or respirator over their nose and mouth in indoor travel or public transportation settings, they protect themselves and those around them.

ImageThe Biden administration left the decision on whether to appeal to Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, and her agency.
The Biden administration left the decision on whether to appeal to Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, and her agency.Credit...Al Drago for The New York Times
The Biden administration left the decision on whether to appeal to Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, and her agency.

The C.D.C. extended the mandate through May 3, and Dr. Jha said in an interview that the additional time would allow the C.D.C. to assess. The question remained unresolved, experts said Wednesday.

The power to impose public health restrictions lies with state and local governments, and the C.D.C. has very limited regulatory authority. Legal experts agree that interstate transportation is an exception. In interviews, several people said that Judge Mizelle had a bad understanding of the law.

The Public Health Service Act of 1944 gave the C.D.C. the authority to make and enforce regulations that are necessary to prevent the introduction, transmission or spread of communicable disease.

The law suggests some steps the C.D.C. could take to prevent the spread of disease.

The C.D.C.'s only options were construed as a narrow interpretation that misunderstands the scope of authority. He said that she likens the mask mandate to a scurvy.

Professor Gostin said that the C.D.C.'s failure to solicit public comment on the mask orderdefies common sense.

ImageThe mask mandate also applied to transportation hubs like airports.
The mask mandate also applied to transportation hubs like airports.Credit...Gabby Jones for The New York Times
The mask mandate also applied to transportation hubs like airports.

Mr. Gostin said that the C.D.C. would have an "extraordinarily good case" on appeal.

Some public health experts argued against extending the transportation mask mandate so as not to cause an appeal of the judge's ruling and potentially cause a higher court to permanently restrict the C.D.C.'s powers.

From a pure public health perspective, I would say let it go, it's not worth the fight.

It could be difficult for the White House and the C.D.C. director to rationalize the decision to appeal the judge's ruling, given that they have increasingly cast mask wearing as a matter of personal preference. On Tuesday, Mr. Biden was noncommittal when asked if people should wear masks on planes.

The C.D.C. changed its guidelines in a way that made it less likely that a county would be considered high risk. Only in high-risk areas can the agency recommend wearing a mask. It says that if you have immune deficiencies or are at high risk for severe illness, you should talk to your health care providers about whether to wear a mask.

According to the C.D.C., counties should decide the level of risk for their residents based on the number of new Covid-related hospital admissions over the past week, the percentage of hospital beds occupied by Covid-19 patients and the rate of new cases.

When these metrics are better, we want to give people a break from things like mask wearing.

Public health experts say it is up to Dr. Walensky to keep her agency's ability to encourage, or even require, mask wearing in the face of any future deadly waves of the virus.

The drama of the judicial opinion shouldn't change what it would have done, said Dr. Gounder.

Sharon and Niraj contributed to the report.