This paper presents some of the concepts that support condition based maintenance (CBM) and relates aircraft wiring to these concepts. Aircraft wiring is considered to be a subset of avionics systems for this presentation. Avionics technology changed little during the 1940s, 1950s and 1960s. Since the 1970s, an almost complete refocus has occurred. New technical advances in avionics systems design and integration have occurred with each new aircraft model introduced to the marketplace. In parallel, a similar technology explosion has also taken place in the commercial computer industry that assisted in the transition of aviation into the digital world. In parallel with the rapid advances in avionics, the airlines' cost cutting strategies, push for high reliability avionics systems and their high degree of systems integration has opened a business opportunity for avionics OEMs to provide maintenance service to their airline customers. This in turn sets the stage for the airline industry to make a transition from reactive and time based maintenance to proactive or CBM practices. Senior airline managers currently stress financial decisions that evaluate the total cost of maintenance and the importance of cost effective maintenance programs. The cost-benefit of individual investments in avionics/wiring test/repair facilities and necessary service parts inventory must be proven. Airline management now stress cost reductions, prudent use of existing capital and an intelligent use of new technology. This is where CBM comes into focus.