As the federal government appeals a court ruling this week that struck down a mask requirement for commercial flights in the United States, some airlines have dropped their mandates and are welcoming back previous travelers who were banned for violating the COVID-19 safety rule.

A judge struck down the mandate on Monday as unconstitutional. The move led some carriers to immediately announce the end of their mask rules, which were in place for more than a year.

The Justice Department, based on a recommendation from the Centers for Disease Control and Prevention, said on Wednesday that it's appealed the ruling. The CDC said that mask compliance is still "necessary for the public health."

In the meantime, some U.S. carriers -- including Delta and United -- have done away with the rule and are allowing travelers who were banned for breaking it to return.

A discarded face mask is seen at Los Angeles International Airport. The mask requirement for all commercial flights in the U.S. has been in effect since February 2021. File Photo by Jim Ruymen/UPI

"On a case-by-case basis we will allow some customers who were previously banned for failing to comply with mask-related rules to fly United again -- after ensuring their commitment to follow all crew member instructions on board," United Airlines said according to USA Today.

Delta Air Lines said that passengers who show an understanding of expected behavior can return. However, it warned that any traveler who disregards any policies will be banned permanently.

"Delta will restore flight privileges for customers on the mask non-compliance no-fly list only after each case is reviewed and each customer demonstrates an understanding of their expected behavior when flying with us," a spokesperson said according to Business Insider.

"Any further disregard for the policies that keep us all safe will result in placement on Delta's permanent no-fly list."

Delta banned about 2,000 passengers for violating the mask rule and United about 1,000.

The federal mask rule was imposed by the CDC and enforced by the Transportation Security Administration in February 2021. A number of incidents on flights involving rebellious passengers -- nearly all of whom were removed from the flights -- have been documented by videos and photos posted online.

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