By David Shepardson

WASHINGTON (Reuters) -The Justice Department on Tuesday asked an appeals court panel to vacate an April 2021 ruling that had declared unlawful a government order requiring masks on airplanes and other transportation modes during the COVID-19 pandemic, saying the issue was now moot because the national emergency was now over.

In January, a three-judge panel of the 11th Circuit Court of Appeals in January heard arguments on the government's appeal of a U.S. district court's ruling that the U.S. Centers for Disease Control and Prevention (CDC) lacked legal authority to issue a nationwide travel mask mandate to combat COVID-19.

The CDC issued the sweeping mask mandate in January 2021, days after President Joe Biden took office. The rules required masks on airplanes, buses, trains, ride-sharing services and at airports and other transportation hubs.

The Justice Department said in a court filing the issue was now moot because of "a fundamental change in public health conditions, as evidenced by the joint resolution of Congress terminating the national emergency."

The plaintiffs who sued to overturn the mask mandate urged the court not to dismiss the case. They included five individuals who did not want to wear masks on flights including a person diagnosed with anxiety and another who suffered from panic attacks related to wearing masks.

Lawyers for the plaintiffs including the group Health Freedom Defense, said in a court filing that dismissing the case "would give CDC the ability to do this -- or something like it -- again while evading review in this court."

This month, Biden revoked requirements that most international visitors to the U.S. be vaccinated against COVID-19 as well as similar rules for federal employees and contractors. The orders were canceled with the expiration of the U.S. COVID public health emergency.

The Biden administration's rules imposed in September 2021 requiring about 3.5 million federal employees and contractors to be vaccinated or face firing or disciplinary action were not enforced for over a year after a series of court rulings.

A report from U.S. lawmakers in October said the Trump administration in 2020 blocked the CDC from adopting a federal transportation mask mandate.

The Justice Department said if the case is not vacated as moot than the court should reverse the judgment on the merits or at a minimum "confine relief to the five individuals" who filed suit.

(Reporting by David Shepardson, Editing by Franklin Paul and David Gregorio)