Glossary · Travel distribution
Fare class (booking class, RBD)
A fare class, also called a booking class or reservation booking designator (RBD), is the single-letter code an airline uses to sell seats within a cabin at a particular price level and set of rules; it controls inventory, while the fare basis code — which almost always starts with the same letter — describes the fare's conditions.
Reviewed 30 Oct 2026
Cabin, booking class and fare basis
| Term | What it is | Example |
|---|---|---|
| Cabin | The physical section of the aircraft | Economy, business |
| Booking class (RBD) | One letter controlling a bucket of seats in a cabin | Y — commonly full-fare economy |
| Fare basis code | The code of the published fare and its rules; starts with the booking class letter | A code beginning with the same letter |
Some letters are used consistently across many airlines — Y for full-fare economy, J for full-fare business, F for full-fare first — but most are airline-specific, so the same letter can mean different things on different carriers.
Why the price jumps when a class sells out
Airlines allocate seats to each booking class and close the cheaper ones as the flight fills or departure nears. When a class closes, the lowest price on offer becomes the next open class up, so the fare steps rather than drifts. This is the mechanism behind much airline dynamic pricing, and why flight prices change as often as they do.
Comparing like with like
A fare's rules — refundability, change fees, advance purchase, minimum stay, combinability — are part of the product. In the EU, Article 23(1) of Regulation 1008/2008 requires that fares offered to the public include the applicable conditions and show the final price including unavoidable taxes and charges.
When collecting prices, store the cabin, fare brand, baggage allowance and the booking class where it is displayed, so a cheap restricted fare is not compared with a flexible one. Airline fares and low-cost carrier fares cover the fields to keep.
FAQ
Questions
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Is fare class the same as cabin class?
No. The cabin is the section of the aircraft, such as economy. The fare class or booking class is a letter that subdivides a cabin's seats into price buckets with different rules, so one economy cabin can be sold under many booking classes.
What does Y class mean on a ticket?
Y is commonly used by airlines for full-fare economy: the most flexible and most expensive economy booking class. Most other letters are airline-specific, so check the carrier's own definitions.
Why do two economy seats on the same flight cost different amounts?
They were sold in different booking classes, each with its own price and rules, and the cheaper classes close as the flight fills. The seat is the same; the fare product and its conditions are not.
Where can I see the booking class of a fare?
Often on the fare details or booking confirmation, and in GDS and agency displays. Many airline websites show a fare brand such as Basic or Flex rather than the letter.
Sources & review
Last reviewed by the ARC Proxies team. Prices are read from the live catalog at build time.
In practice