The Tokyo Convention of 1963 establishes jurisdiction over offenses while an aircraft is in flight and grants a wide sprectrum of powers to the aircraft commander to restrain a passenger. The Hague Convention of 1970 obliges states to punish the unlawful seizure of aircraft with severe penalties and to either extradite the offender or try him. The Montreal Convention of 1971 establishes a system of suppression of acts against aircraft, covering mostly acts on the ground that might endanger an aircraft in flight, and requires states to take practicable measures to prevent such offenses. In the past few years the number of countries adhering to these pacts and instituting improved security measures has increased significantly. Accompanying this trend has been a downward trend in acts of unlawful interference and seizure of aircraft to 147 in the 1978-1980 period compared to 245 in the 1969-1971 period. Nevertheless, only steadfast efforts by all nations can complete the job of eliminating unlawful interference with international civil aviation. (Author abstract)