With three years of in-service data compiled, early analysis shows that operators of the new 737s are starting to see a 15 percent reduction in maintenance costs, a goal that was established when the program was launched in 1993. Reducing fleet costs is a key issue that directly affects every airline's bottom line. Fleet maintenance costs can range from 10 to 20 percent of total airplane-related operating costs. Since many of the larger airlines have maintenance budgets in excess of $1 billion, the savings can be substantial.