The top three U.S. airlines are telling flight attendants not to force passengers to comply with new policy that requires face coverings on flights.   

The directive comes just weeks after major U.S. airlines announced that face masks would be required to fly.

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American, Delta, and United flight attendants are being told to simply encourage passengers to follow the rules and not to enforce them, as first reported in Reuters.

And while cabin crew cannot force a passenger to put on their face mask during the flight, all carriers have been told they can deny boarding to passengers without one.

“Once onboard and off the gate, the face-covering policy becomes more lenient. The flight attendant’s role is informational, not enforcement, with respect to the face-covering policy,” American told its pilots.  “Bottom line to the pilots: a passenger onboard your aircraft who is being compliant with the exception of wearing a face covering is NOT considered disruptive enough to trigger a Threat Level 1 response,” the message continues referring to intentional disruptions that would make the pilot divert the flight.

A United spokeswoman said any non-compliance by travelers would be addressed at the gate and its flight attendants had been counseled to use their “de-escalation skills” on the aircraft and to reseat any passengers as needed.

Delta confirmed that it has a similar policy to United.

All three airlines have exemptions for young children or people with medical conditions or disabilities, and when people are eating or drinking.