Air Carrier Access Act Technical Assistance Manual (2005)

If the Passenger Poses a Direct Threat to the Health and Safety of Others

If, in your estimation, a passenger with a communicable disease or infection poses a direct threat to the health or safety of other passengers, you may (i) refuse to provide transportation to that person; (ii) require that person to provide a medical certificate stating that the disease at its current stage would not be transmittable during the normal course of a flight or, if applicable, describing measures that would prevent transmission during the flight [Sec. 382.53(c)]; or (iii) impose on that passenger a special condition or restriction (e.g., wearing a mask). You must choose the least restrictive of the three options set forth above that would accomplish the objective. [Sec. 382.51(b)(4)]

At all times, as a matter of good customer service, you should treat the passenger with courtesy and respect.