Illegal acts of violence, detention or any act of depredation committed outside the jurisdiction of any State, for private ends, by the crew or the passengers of a private ship or a private aircraft is piracy if it is directed against their own or other ships or aircraft, or against persons or property onboard, overboard, or ashore (where there is no effective jurisdiction). Pirates may be abetted by persons performing acts of voluntary participation in the operation of a ship or of an aircraft with knowledge of facts, making it a pirate ship or aircraft, or by any act of inciting or of intentionally facilitating participation in piracy. Piracy can be committed with the use of a warship, government ship or government aircraft whose crew has mutinied and taken control. The terms ship and aircraft may also be specified as to mean 'any sea-going vessel' (submarines, etc) and 'any air- or spacecraft'. Hybrid vessels such as sea-based air- or spacecraft, and any unmanned vessels or craft controlled remotely, may be involved in future piratical acts

The modern term highjacking is the unlawful seizure of a vehicle, plane, or boat, by force or threat and as such is equivalent to piracy. Recently, hijacking has become synonymous with skyjacking, and especially refers to those who skyjack to make a political point, to seek asylum, to gain revenge or the release of prisoners, or to obtain other concessions

In the period from 1984 to 1993 some 480 pirate raids were registered by the International Maritime Organization and the number is increasing annually. This is believed to represent approximately 50% of the actual total of attacks. The majority of attacks tend to be in the South China Sea and North Asia. The most recent widespread and publicized piracy concerns the piratical atrocities committed against the Indo-Chinese boat people in the aftermath of the Vietnam war. In 1994 Chinese gunboats with what appeared to be military personnel were alleged to have held up several ships which were then stripped of their cargo. It was unclear whether they were official sponsored or were the activities of renegade officers