All passengers on public conveyances (e.g., airplanes, ships*, ferries, trains, subways, buses, taxis, ride-shares) traveling into, within, or out of the United States (including U.S. territories) as well as conveyance operators (e.g., crew, drivers, conductors, and other workers involved in the operation of conveyances), regardless of their vaccination status, are required to wear a mask over their nose and mouth. Unless otherwise required by the operator, or federal, State, tribal, territorial, or local government, people are not required to wear a mask when located in outdoor areas of a conveyance (if such outdoor areas exist on the conveyance).
https://www.cdc.gov/quarantine/masks/mask-travel-guidance.html
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