Some of those Mercury engineers later formed a new division within IBM, where "another early and striking example of a major IID success the very heart of NASA’s space shuttle software—the primary avionics software system, which [they built from 1977 to 1980. The team applied IID in a series of 17 iterations over 31 months, averaging around eight weeks per iteration. Their motivation for avoiding the waterfall life cycle was that the shuttle program’s requirements changed during the software development process."