A Combat System Officer (or CSO differs from CSOp) is a member of an aircrew in the United States Air Force and is often the mission commander in many multi-crew aircraft. The Combat System Officer manages the mission and integrates systems and crew with the aircraft commander to collectively achieve and maintain situational awareness and mission effectiveness. CSOs are trained in navigation, the use of the electromagnetic spectrum, and weapon system employment. Aircrew responsibilities include mission planning, mission timing, weapons targeting and employment, threat reactions, aircraft communications, and hazard avoidance.