The role of software as the most critical part of weapons systems is growing. As an example, 80% of the functionality in modern-day aircraft, like the F-35 Joint Strike Fighter (JSF), is dependent on software. Consequently, software has become a major cost driver in weapons system, development and life-cycle support. Logisticians play a major role in establishing and executing the weapons systems support environment as well as estimating the support costs. Software growth will continue as technology advances, so it is critical for logisticians to have the tools necessary to make informed decisions relative to the support of software-intensive systems.