If you plan on flying anywhere now, or sometime soon, US airlines have an important and mandatory rule for you: “Wear a mask in the airport and on the plane.” Or else.

The airlines are not messing around. All but three of them – Allegiant, Delta and Hawaiian – are not exempting passengers on the basis of medical condition or disability. And there are stipulations to the exemptions. Budget carrier Sun Country says guests who cannot wear a mask will be expected to wear face shields.

In late July, a Delta flight set to depart from Detroit Metropolitan Airport returned to the gate to remove two passengers who refused to wear masks. On 11 August, Alaska Airlines deplaned and delayed a flight out of Spokane because several passengers refused to wear their masks.

Don’t want to be that passenger?’

Runway Girl Network has put together links and brief highlights of the mask policies for US airlines. If you are flying, be sure read your airline’s policy thoroughly and check for updates as guidelines, enforcement rules and policies regarding infringement are being refined all the time.

American Airlines

As of 19 August, American Airlines will no longer allow face coverings with exhaust valves or vents. The updated policy requires that face coverings be worn correctly (covering the nose and mouth) and prohibits masks made of materials such as mesh or lace fabric.

“Those unwilling to comply with American’s face covering policy at any time during their journey may be denied boarding or barred from future travel for the duration of this policy,” the airline’s policy states.

Alaska Airlines

Alaska Airlines updated it mask policy on 7 August to clarify that passengers age 2 and over are required to wear face coverings, with no exceptions.

“If a guest is unwilling or unable to wear a mask for any reason while at the airport, they will not be permitted to travel,” Alaska Airlines says in a statement, “If a guest refuses to wear a mask after boarding their flight, they will be suspended from future travel.”

Allegiant Air

Passengers on Allegiant Air claiming to be exempt from wearing a mask due to medical conditions must provide documentation from a medical physician to the gate agent one hour before departure.

Delta Air Lines

Delta Air Lines, which has already put more than 100 people on its ‘no fly’ list for refusing to comply with the airlines’ mask rules, does not allow masks with exhaust valves and doesn’t allow plastic faces shields to be used instead of masks.

Delta suggests that customers “reconsider travel” if they have an underlying conditions that prevents them from wearing a face mask or be prepared to complete a ‘Clearance-to-Fly’ examination at the airport that may take over an hour.

Frontier Airlines

Frontier Airlines says: “Face coverings must fit snugly over your nose and mouth and be secured under the chin. Open-chin triangle bandanas, face covering containing vents, valves or mesh material, and face shields are not acceptable as face covering.”

The only exception is for children under the age of 2, says the carrier.

Hawaiian Airlines

Face masks must effectively cover the mouth and nose, says Hawaiian Airlines. But young children unable to keep a face covering on, or guests with a medical condition or disability preventing its use, will be exempt from the policy.”

JetBlue Airways

JetBlue Airways says: “Masks with vents or exhalation valves are not permitted. Plastic face shields may be worn in addition to a face covering but not in place of one.”

JetBlue suggests that customers with conditions that prevent them from wearing a face mask “postpone travel until this temporary requirement is no longer in place.”

Southwest Airlines

Southwest Airlines’ stance is clear. Not acceptable: masks with holes in the covering, including those with exhalation valves or made of material like mesh or lace fabrics and masks that cannot be secured under the chin, such as bandanas and face shields.

“Southwest will temporarily refuse to transport any passenger who is unable to wear a mask even if the customer has a verifiable medical condition that prevents them from wearing a mask,” it says.

Spirit Airlines

Spirit Airlines says: Guests over age two “unable to wear an appropriate face covering for any reason, including medical, will not be permitted to travel with us at this time.”

Sun Country

Sun Country will accept face shields. It says: “Guests who cannot wear face masks due to medical reasons will be expected to wear face shields.”

United Airlines

United Airlines advises: “Your face covering must fully cover your nose and mouth and may not have any vents or openings. A face shield alone does not count as a face covering.”

If you refuse to follow the airline’s face covering policy, you could “lose your travel privileges on United for a certain period of time”, it warns.