Avionics is a portmanteau word meaning "aviation electronics." It is a term that has evolved over the last 40 years as airplane instrumentation has evolved from mostly mechanical to largely electronic. Today, avionics makes up the large part of the cost of any aircraft. Guidance and navigation systems are integrated. Communications includes public address systems for communicating with passengers, intercoms for communicating with flight crews, and radio or SatCom for communicating with ground personnel. In addition, planes today have weather radar, lightning detectors, automatic flight control systems, and collision-avoidance systems. All of these systems must work in tandem in order for the plane to fly.