Revenue management has three levels: strategic, tactical and booking control. Revenue management strategy is the level, where market segments and the price, set for that particular segment, are determined. This is done mainly annually. Revenue management tactics is the process of determining and updating the limit of how much unit of the capacity can be sold to a particular fare class. This is done frequently, in most cases daily or weekly. In the following chapters I am going to focus on this second level of revenue management. Booking control has to be done in real time. When a booking request arrives for a flight, we have to decide to accept it, or maybe refuse it and wait for another one that can increase the profit more. The decision is made with the help of a reservation system. This system has the booking limits for all the fare classes. Airline companies determine the number of available discount seats with the help of booking limits. These are controls that limit the amount of capacity that can be sold to any particular class at a given point in time. If the demand reaches this limit, the class needs to be closed to any other customer from the same class. There are two kinds of booking limits: