The DOJ will appeal the recent mask ruling by a federal judge

A person is wearing a mask while walking outside in Philadelphia.

Matt Rourke/AP

Don't put the masks away just yet.

The US Department of Justice is appealing the decision by a federal judge that voided the mask mandate for public transportation.

The Centers for Disease Control and Prevention determined that wearing a mask is necessary to protect the public health, according to an agency spokesman.

After checking with the CDC, the Biden administration said it may appeal the decision by the District Judge.

The decision came two days after the CDC was ruled to have failed to follow proper rulemaking procedures.

Many airlines stopped requiring passengers to wear masks after Monday's decision.