Many big US airlines are bringing in new health and safety policies for both passengers and cabin crew this week.
Other carriers around the world are also making mask wearing mandatory for when they restart flights.
While around 90% of international flights have been cancelled, airlines hope to gradually resume air travel starting this month.
From Monday, US carrier Delta said it requires passengers to wear a mask or other face covering in the check-in area, premium lounges, boarding gate areas and onboard planes for the whole flight.
American Airlines and United have also said that they will start requiring masks for passengers, along with cabin crew. The carriers say these are temporary measures as they slowly resume flights.