Scheduled airlines do not sell every seat on a flight for the same price. Each Class (First, Business, Economy) is divided into fare classes. This division is not fixed and depends on route popularity, holidays, time of flights and many other factors.

This means that if the airline did its sums right, the later you book, the more expensive the ticket price. Fare classes also determine if you are able to receive a check-in staff discretionary upgrade to premium economy or even first or business class.

No amount of charm and wearing expensive suits will get you that upgrade if you have the wrong fare class ticket. This also explains why a group booking may be more expensive than pricing for one. There may not be enough seats left in the cheapest class for your group, so you move up in fare class until there are enough tickets for your group.

So when looking for prices, you are really looking for the lowest fare class available for your flight. This is why you should be flexible with your flight dates, as a day earlier or later could get you that heavily discounted fare class.

Fare Class Explanation
A First Class Discounted
B Economy Discounted
C Business Class
D Business Class Discounted
E Shuttle Service (No reservation allowed), or Economy Discounted (or Premium Economy)
F First Class
G Conditional Reservation
H Economy Discounted
I Economy Discounted
J Business Class Premium
K Economy Discounted
L Economy Discounted
M Economy Discounted
N Economy Discounted
P First Class Premium
Q Economy Discounted
R Was supersonic now First Class Suites on Airbus A380
S Economy (or Premium Economy)
T Economy Discounted
U Shuttle Service (No res. needed/Seat guaranteed)
V Economy Discounted
W Economy Premium (or Premium Economy)
X Economy Discounted
Y Economy
Z Business Class Discounted

A full fare, 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 S, W, or to confuse things even more, may use other letters.

T or W which are heavily discounted fares, will not permit cabin upgrades, refunds, or reservation changes, and may require Internet booking. They may also be exempt from frequent flyer schemes, or may impose other restrictions. Other fare codes are restricted for use by consolidators, group charters, or travel industry professionals.

Low-cost (or no frills) carriers have simplified the fare classes they use to a handful of cases. So in economy a passenger with a ‘Y’ ticket will sit next to same one with a ‘W’ ticket, eat the same food and get the same service, but would have paid £100’s more for their ticket. If you are unsure of your flight dates, then a ‘Y’ may work out cheaper than a ‘W’ if you have to change your flight.