Biden’s statement was at odds with his administration’s official guidance.

The Justice Department said it would appeal a Monday ruling by US District Judge Kathryn Kimball Mizelle that the 14-month-old directive was unlawful if the Centers for Disease Control and Prevention determined the mandate was needed to protect public health.

The ruling overturned a key presidential effort to reduce the spread of Covid-19.

“If CDC concludes that a mandatory order remains necessary for the public’s health after that assessment, the Department of Justice will appeal the district court’s decision,” the Justice Department said in a statement.

The CDC still advises people to wear masks on public transit, White House spokesperson Jen Psaki noted shortly before Biden’s comment.

“We’re continuing to encourage people to wear masks,” Psaki told reporters on Air Force One.

After landing in New Hampshire, a short while later, Biden, asked whether people should continue to wear masks on planes, said, “It’s up to them.”

Monday’s court decision, made in response to a lawsuit filed last year in Tampa, Florida, means the CDC’s public transportation masking order is no longer in effect, a US official said.

It comes as Covid-19 infections are rising in the US, and more than 400 people are dying daily from the airborne disease, based on the latest seven-day average.

The ruling followed a string of judgments against Biden administration directives to fight the infectious disease that has killed nearly 1 million Americans, including vaccination or Covid testing mandates for employers.

“Public health decisions shouldn’t be made by the courts. They should be made by public health experts,” Psaki said.