Travel class

                                                                                                                
Airlines traditionally have three travel classes, although many airlines are eliminating first class from international flights and now offer business class as the highest level of service:

• First Class, generally the most expensive and most comfortable accommodations available.
• Business Class, high quality, traditionally purchased by business travellers (sometimes called executive class)
• Premium Economy, slightly better Economy Class seating (greater distance between rows of seats; the seats themselves may or may not be wider than regular economy class)
• Economy Class (also known as coach class or travel class), basic accommodation, commonly purchased by leisure travellers

Three-cabin configuration is found on international and transcontinental flights. For shorter distances, most airlines fly a two-cabin plane, featuring only Business and Economy Class cabins. The short-haul Business Class cabin is usually designated as "First Class" in the USA (domestic).

Some airlines merge their international First and Business classes into a premium business product with the consequence of lost exclusivity (for example, Continental Airlines has a BusinessFirst class), whereas others supplement the Business Class cabin with a Premium Economyclass cabin. Some airlines, such as Japan Airlines, Singapore Airlines and Lufthansa, offer flights with only a Business Class service.

Some low-cost carriers and regional affiliates of major carriers only provide an Economy Class. The costs of extra services and amenities afforded to the premium cabins is eliminated, and more seats can be installed on an aircraft.

Fare class

Within each travel class there are often different fare classes, relating to ticket or reservation restrictions and used to enhance opportunities forprice 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 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 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.

First class codes

• F, A, P, R

On USA domestic flights, F commonly indicates first class on a two-cabin plane. If a three-cabin aircraft is used, P (for "premium") may be used to distinguish the higher level of service in first class. The R code indicated supersonic transport and was no longer used after the retirement of the Concorde, however with the introduction of the new Airbus A380, Singapore Airlines and Qantas have re-introduced the R class to distinguish a higher class than regular First Class. The A and P codes may indicate a first class ticket whose fare is reduced due to restrictions on refunds, advance reservation requirements, or other terms.

The codes in short:

• F = Full-Fare First Class
• P = First Class (some airlines use this code for Business class. Jet Airways of India, for instance).
• A = First Class Discounted
• R = First Class Suites (currently only Airbus A380, and formerly Supersonic Concorde),

Business class codes

• C, J, D, I, Z

On many airlines, C or J indicate full fare business class, whereas discounted and thus restricted and typically non-upgradeable fares are represented by D, I or Z.

The codes in short:

• C, J = Full-fare Business Class,
• D, I, Z = Business Class Discounted,

Economy class codes

• Full fare: Y, B
• Standard fare: M, H
• Special or discount fares: G, K, L, N, O, Q, S, T, U, V, W, X

On most airlines, unrestricted economy ticket is booked as a Y fare. Full fare tickets with restrictions on travel dates, refunds, or advance reservations are commonly classed as B, H, or M, although some airlines may use H, V, or others. Heavily discounted fares, commonly O, T or X, will not permit cabin upgrades, refunds, or reservation changes, may restrict frequent flyer program eligibility, and/or impose other restrictions. Other fare codes such as X are restricted for use by consolidators, group charters, or travel industry professionals. However on some airlines W or X is used for frequent flier program award redemptions.

Airlines that offer premium economy cabins have also specified certain codes for fares in the upgraded economy cabin, which are usually S (which in this case often stands for 'Supercomfort'), W, or E.

Premium economy codes:

• E, H, K, O, U, W, T

Most low-cost carriers have greatly simplified the fare classes they use to a handful of cases, unlike the dozens employed by a traditional airline. While some traditional carriers have followed, others continue to utilize price discrimination over commoditization.

The codes in short:

• B = * Q = Economy/Coach Discounted

             Source:-wikipedia