Aviation law is the branch of law that concerns flight, air travel, and associated legal and business concerns. Some of its area of concern overlaps that of admiralty law and, in many cases, aviation law is considered a matter of international law due to the nature of air travel. However, the business aspects of airlines and their regulation also fall under aviation law. In the international realm, the International Civil Aviation Organization (ICAO) provides general rules and mediates international concerns to an extent regarding aviation law. The ICAO is a specialized agency of the United Nations.