(FORTUNE Magazine) – THE GLOCK 17 PISTOL is the latest terrorist weapon to menace air travelers around the world. The simple, lightweight, Austrian-made gun has a suggested retail price of $443 and has 32 pieces -- many of them plastic, which does not show up as clearly as metal on X-ray machines. It can be taken apart or reassembled in less than a minute. Airport security officials fear that terrorists could disguise the pieces in luggage and smuggle them through X- ray inspection. Libya's Muammar Qaddafi reportedly has ordered up to 100 Glock 17s. A new X-ray system introduced in January by American Science & Engineering Inc. of Cambridge, Massachusetts, may be the traveler's best defense. The company (1985 sales: $22.5 million), which made the X-ray telescope used to discover black holes in space, has devised an X-ray technique that makes a concealed Glock 17 easier to spot. Like a conventional X-ray, AS&E's ''Z system'' detects high-density materials like metals, which appear dark on a screen because they absorb X-rays. But the Z system also picks up lower- density substances like plastics and narcotics, which scatter X-ray beams in all directions, by pinpointing the source of the scattering. AS&E's device scans the contents of a suitcase or package with a narrowly focused ''flying spot'' X-ray beam rather than a conventional fanlike beam. As the beam strikes the suitcase, separate detectors display different images simultaneously on two television monitors (see photographs). One screen shows the high-density materials -- for example, a radio and a traveling case. The other reveals the plastic handle of a Glock 17 hidden beside the radio. The weakest link in airport security remains the inspectors, who get bored and overlook suspicious objects. Theofolus Tsacoumis, a retired Federal Aviation Administration security program manager, believes semiautomatic sensing devices might recognize objects and alert inspectors, although the systems require complex computer programs and are at least three years off. Westinghouse and Science Applications International Corp. of La Jolla, California, among others, are working on these devices. Until they come along, airports will have to depend entirely on human operators. Despite the $55,000 price of AS&E's Z system, nearly twice that of the average airport X-ray machine, Finland and France have ordered it, and other countries including Israel and Egypt are negotiating. AS&E has promised delivery within six weeks, which may reassure summer travelers. AS&E stockholders are feeling reassured too: the stock has climbed 58%, from $4.75 to $7.50 a share, since January 1.