IATA defines the reservations booking designator as the code used in reservations to identify a compartment on the aircraft, a special inventory control or both. Its data model describes booking classes as giving access to inventory, applying filed fares and identifying cabin entitlement, with several typically defined for each cabin. IATA adds that the booking class is usually determined by the fare basis.

One cabin, many classes

A cabin is not a booking class. Virgin Atlantic’s Flying Club, for example, awards 200 tier points for Upper Class booked in J, C, D or I, but 100 tier points in Z or G. A fare also needs seats in its class: Delta says its Delta Comfort fares can only be bought when both the W or S class and the matching Delta Main class are available.

Letters differ between airlines

Airlines share some letters, such as J, C and D for business class, but each sets its own classes, so other letters can mean different things. W is a Premium class on Virgin Atlantic, while Delta books its Delta Comfort fares, an extra-legroom product built on Delta Main, in W or S. Virgin Atlantic’s own mapping table books its Economy Delight class V into Delta’s W or S on transatlantic flights operated by Delta.

Why it matters for agents

• When one airline sells another’s flights under a codeshare or interline agreement, their classes can differ. Virgin Atlantic, for example, publishes tables matching its booking classes to its partners’ classes, so agents know which class to book.

• The term fare class is also used. Delta, for example, uses it for the first letter of the fare basis, which usually matches the booking class but not always.