The Biden administration will no longer impose an obligation to wear masks on public transportation, after a federal judge in Florida ruled the directive was illegal, undermining key White House efforts to reduce the spread of Covid-19.

All major US airlines have welcomed the move by deciding they will no longer require wearing masks.

A federal judge in Florida, Kathryn Kimball Mizelle, ruled Monday that the 14-month directive was illegal, thwarting key White House efforts to reduce the spread of Covid-19.

Judge Mizelle said the U.S. Centre for Disease Control and Prevention (CDC) exceeded its authority by imposing the obligation to wear masks, did not seek public opinion and did not properly explain its decisions.

The verdict comes as the number of cases in the United States begins to rise again, with an average of 36,251 new infections every day and 460 deaths a day, compared to the seven-day average - currently the highest number of Covid-19 deaths in the world.

The White House called the verdict "disappointing."

U.S. passenger traffic has averaged about 89 percent of pre-pandemic levels since mid-February.

With the resurgence of Covid-19 cases, the abolition of the obligation to wear masks could make some passengers distrustful, while some could be encouraged to fly again.