Aircraft hijacking (also air piracy or aircraft piracy, especially within the special aircraft jurisdiction of the United States, and informally as skyjacking) is the unlawful seizure of an aircraft by an individual or a group. In most cases, the pilot is forced to fly according to the orders of the hijackers. Occasionally, however, the hijackers have flown the aircraft themselves, such as the September 11 attacks. In at least three cases, the plane was hijacked by the official pilot or co-pilot.
Unlike the typical hijackings of land vehicles or ships, skyjacking is not usually committed for robbery or theft. Most aircraft hijackers intend to use the passengers as hostages, either for monetary ransom or for some political or administrative concession by authorities. Various motives have driven such occurrences, including demanding the release of certain inmates (notably IC-814), highlighting the grievances of a particular community (notably AF 8969), or political asylum (notably ET 961). Hijackers also have used aircraft as a weapon to target particular locations (notably during the September 11, 2001 attacks).
Hijackings for hostages commonly produce an armed standoff during a period of negotiation between hijackers and authorities, followed by some form of settlement. Settlements do not always meet the hijackers' original demands. If the hijackers' demands are deemed too great and the perpetrators show no inclination to surrender, authorities sometimes employ armed special forces to attempt a rescue of the hostages (notably Operation Entebbe).
The so-called "Golden Age" of skyjacking in the United States ran from 1968 through 1979, and into the 1980s in parts of the world, with attacks tapering off after as new regulations made boarding aircraft with weapons extremely difficult.