into losing $50 million a month... We had been profitable from the day we started until American came at us with Ultimate Super Savers." in the book Revenue Management by Robert G. Cross, Chairman and CEO of Revenue Analytics. The yield management systems developed at American Airlines were recognized by the Edelman Prize committee of INFORMS for contributing $1.4 billion in a three-year period at the airline. Yield management spread to other travel and transportation companies in the early 1990s. Notable was implementation of yield management at National Car Rental. In 1993, General Motors was forced to take a $744 million charge against earnings related to its ownership of National Car Rental. In response, National's program expanded the definition of yield management to include capacity management, pricing and reservations control. As a result of this program, General Motors was able to sell National Car Rental for an estimated $1.2 billion. Yield management gave way to the more general practice of revenue management. Whereas revenue management involves predicting consumer behavior by segmenting markets, forecasting demand, and optimizing prices for several different types of products, yield management refers specifically to maximizing revenue through inventory control. Some notable revenue management implementations include the NBC which credits its system with $200 million in improved ad sales from 1996 to 2000, the target pricing initiative at UPS, and revenue management at Texas Children's Hospital. Since 2000, much of the dynamic pricing, promotions management and dynamic packaging that underlie e commerce sites leverage revenue management techniques. In 2002 GMAC launched an early implementation of web based revenue management in the financial services industry. There have also been high-profile failures and faux pas. Amazon.com was criticized for irrational price changes that resulted from a revenue management software bug. The Coca-Cola Company's plans for a dynamic pricing vending machine were put on hold as a result of negative consumer reactions. Revenue management is also blamed for much of the financial difficulty currently experienced by legacy carriers. The reliance of the major carriers on high fares in captive markets arguably created the conditions for low-cost carriers to thrive. Use by industry There are three essential conditions for yield management to be applicable: That there is a fixed amount of resources available for sale. That the resources sold are perishable (there is a time limit to selling the resources, after which they cease to be of value). That different customers