Fare basis code

A fare basis code (often just referred to as a fare basis) is an alpha or alpha-numeric code used by airlines to identify a fare type and allow airline staff and travel agents to find the rules applicable to that fare. Fare codes start with a letter called a booking code or class, which almost always matches the letter code that the reservation is booked in. Other letters or numbers may follow. Typically a fare basis will be 3 to 7 characters long. but can be up to 8.