On June 29, 1993, President William J. Clinton transmitted to the Senate, for advice and consent to ratification, the Convention on the Marking of Plastic Explosives for the Purpose of Detection, with Technical Annex, done at Montreal on March 1, 1991. The Convention is aimed at precluding the recurrence of incidents such as the terrorist bombings of Pan Am Flight 103 over Lockerbie, Scotland, in December 1988, and UTA (Union de Transports Aériens) Flight 172 over Niger in September 1989, as well as other incidents in which plastic explosives were utilized. To this end, it requires states producing such explosives to mark them at the time of manufacture with a substance enhancing their detectability by commercially available mechanical or canine detectors. The Convention also requires states to ensure the implementation of controls over the sale, use, and disposition of marked and unmarked plastic explosives.