If you plan to board a United or Delta Flight at Billings Logan International Airport on Monday, make sure you pack a face mask in your carry on.
On May 4, passengers on both airlines must wear a face mask or appropriate face covering.
Frontier will require masks on May 8. American and Alaska Airlines implement the rule on May 11.
"For the future, this will be the new normal. And frankly, if the airlines are going to entice folks back into the sky they need to do this so people can feel safe." said Kevin Ploehn, Billings director of aviation and transit.
Ploehn also recommended that passengers bring their own masks. If they did not, the airlines should have one available for them.
People unable to keep a face covering in place, including children, are exempt.
The operations directive comes as the number of people flying out of Billings is down 92 percent in April compared to last year.
Ploehn estimates only 2,800 people went through screening last month compared to over 36,000 in April last year.