14 CFR §382.155

1. (a)As a carrier providing service using aircraft with 19 or more passenger seats, you must respond to written complaints received by any means (e.g., letter, fax, e-mail, electronic instant message) concerning matters covered buy this part.
2. (b)As a passenger making a written complaint, you must state whether you had contacted a CRO in the matter, provide the name of the CRO and the date of the contact, if available, and enclose any written response you received from the CRO.
3. (c)As a carrier, you are not required to respond to a complaint postmarked or transmitted more than 45 days after the date of the incident, except for complaints referred to you by the Department of Transportation.
4. (d)As a carrier, you must make a dispositive written response to a written disability complaint within 30 days of its receipt. The response must specifically admit or deny that a violation of this part has occurred.
   1. (1)If you admit that a violation has occurred, you must provide to the complainant a written statement setting forth a summary of the facts and the steps, if any, you will take in response to the violation.
   2. (2)If you deny that a violation has occurred, your response must include a summary of the facts and your reasons, under this part, for the determination.
   3. (3)Your response must also inform the complainant of his or her right to pursue DOT enforcement action under this part.