Foreign Object Damage, or FOD, is a major problem for aircraft. It can be caused by anything that is not part of the aircraft, including tools, parts, debris, and even people. Foreign Object Damage can damage vital components, cause systems to fail, and even cause crashes. In addition to being a safety hazard, FOD is also expensive to repair. Aircraft operators must take steps to prevent FOD, such as maintaining a clean work area and using covers or restraints on loose objects. If FOD does occur, it must be promptly removed to avoid further damage.