courtesy Transportation Security Administration
Investigation subsequently discovered that the explosion was caused by Semtex (a plastic explosive) connected to a timer triggered by changes in barometric pressure, packed inside luggage that had been smuggled onto the plane.
In response to heightened concern over air cargo security, the 1990 Aviation Security Improvement Act was passed.
Among the requirements of the Act were improved background checks for airport security staff, and baggage matching procedures to ensure that all baggage loaded onto a passenger flight 'matched' a passenger on board.
The use of plastic explosives also encouraged the use of computer tomography scanners, known as CT scanners to investigate the contents of checked baggage. This X-ray scanner produces three-dimensional images of bag contents, but they are slow and only used to check previously identified potentially suspicious baggage.
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