14 C.F.R. § 382.21 – May carriers limit access to transportation on the basis that a passenger has a communicable disease or other medical condition?

(a) You must not do any of the following things on the basis that a passenger has a communicable disease or infection, unless you determine that the passenger's condition poses a direct threat:
1. (1) Refuse to provide transportation to the passenger;
2. (2) Delay the passenger's transportation (e.g., require the passenger to take a later flight);
3. (3) Impose on the passenger any condition, restriction, or requirement not imposed on other passengers; or
4. (4) Require the passenger to provide a medical certificate.
(b) In assessing whether the passenger's condition poses a direct threat, you must apply the provisions of § 382.19(c)(1)-(2) of this subpart.
1. (1) In making this assessment, you may rely on directives issued by public health authorities (e.g., the U.S. Centers for Disease Control or Public Health Service; comparable agencies in other countries; the World Health Organization).
2. (2) In making this assessment, you must consider the significance of the consequences of a communicable disease and the degree to which it can be readily transmitted by casual contact in an aircraft cabin environment.
  Example 1 to paragraph (b)(2):The common cold is readily transmissible in an aircraft cabin environment but does not have severe health consequences. Someone with a cold would not pose a direct threat.
  Example 2 to paragraph (b)(2):AIDS has very severe health consequences but is not readily transmissible in an aircraft cabin environment. Someone would not pose a direct threat because he or she is HIV-positive or has AIDS.
  Example 3 to paragraph (b)(2):SARS may be readily transmissible in an aircraft cabin environment and has severe health consequences. Someone with SARS probably poses a direct threat.
(c) If a passenger with a communicable disease meeting the direct threat criteria of this section gives you a medical certificate of the kind outlined in § 382.23(c)(2) describing measures for preventing transmission of the disease during the normal course of the flight, you must provide transportation to the passenger, unless you are unable to carry out the measures.
(d) If your action under this section results in the postponement of a passenger's travel, you must permit the passenger to travel at a later time (up to 90 days from the date of the postponed travel) at the fare that would have applied to the passenger's originally scheduled trip without penalty or, at the passenger's discretion, provide a refund for any unused flights, including return flights.
(e) If you take any action under this section that restricts a passenger's travel, you must, on the passenger's request, provide a written explanation within 10 days of the request.