restrictions and used to enhance opportunities for price discrimination. Passengers within the same travel class receive the same quality of accommodation and may indeed sit next to each other; however, the price or restrictions they face for that accommodation will vary depending on the fare class. Fare classes may also vary by how far ahead the ticket must be purchased, or how long the length of stay is. For example, full fare economy class passengers (booking code Y) are usually able to make changes to their reservation, while discount economy class passengers in the lowest booking code usually have tickets that are non-refundable, non-upgradeable, non-transferable, or non-changeable without a hefty fee.
Airline fare classes are commonly indicated by letter codes, but the exact hierarchy and terms of these booking codes vary greatly from carrier to carrier.