On his first day in office last week, new President Joe Biden did what many airlines and aviation executives were begging for for months – Biden signed an executive order making it mandatory to wear a face mask inside all airports and on airplanes.

But airlines have already been vigilant on their own to help mitigate the spread of the COVID-19 pandemic.

In a great story by Business Insider , more than 2,500 passengers have already been banned collectively by U.S. airlines as carriers wage a daily battle with unruly fliers who refuse to wear a mask .

Delta Air Lines leads the way, having banned 880 passengers – including six on a single flight where Sen. Mitt Romney (R-Utah) was harassed.

As Business Insider noted, despite the fact that the pandemic has limited airline capacity to less than 50 percent of what it was in 2018, the airlines look at this as addition by subtraction – the loss of travelers who are banned is outweighed by the reality that masks are helping mitigate the virus, perhaps enticing more passengers to fly who had been concerned about safety.

Here's what domestic carriers have done so far and how US airlines are stacking up when it comes to enforcing mask policies.

Allegiant The last major airline to require passengers to wear masks, Allegiant has only banned 15 passengers.

Hawaiian Airlines So far, Hawaiian has banned 56 passengers for non-compliance.

JetBlue As of January 20, a total of 115 passengers have gotten the boot.

Alaska Of the 328 total who have been banned, 14 passengers were banned on a single flight from Washington, D.C. to Seattle for non-compliance, as well as rowdy behavior.

Spirit Spirit Airlines has banned "about 400" passengers for mask non-compliance, a spokesperson told Insider.

Frontier More than 500 passengers have been added to what Frontier calls its "prevent departure list."

United United Airlines is reporting 613 banned passengers for mask non-compliance as of January 15.

Delta As previously mentioned, Delta has banned the most passengers with 880.

American Airlines, Southwest Airlines and Sun Country Airlines did not provide specific data on how many passengers were banned due to mask non-compliance.