What do booking codes mean within cabin classes?

All the booking classes are used for seat inventory control. So Airlines can charge different types of passengers for different price for exactly the same service. Let's just take coach class cabin for example. Airlines allocate a numbers of coach cabin seats in different groups represented by Alphabets (class); for combinations of below purposes: 1. Price - Airlines want to ensure high load factor. One of the ways to do it is to encourage buying in advance. The cheaper booking classes usually get sold out first. When the demand is high late buyers will have to up-sell to higher fare. On the other hand if a flight has a lot of empty seats, airlines may move the inventory to lower group (class) to push sales. 2. Restrictions - More expansive group (class) are less restrictive. Discounted fares often require weekend stay because the airlines know business travelers are less likely to stay over weekend. Business travelers will likely forced to book in higher group (class) paying more to ...  more