There are two basic factors that strongly indicate that it was highly unlikely that TWA 800 was brought down by a missile fired by terrorists:
1. If it were terrorists, then they picked a terrible location from which to attempt something like this. TWA 800 was flying at an altitude of something like 13,000 feet at the time it was "hit," which means it would have been at or near the limit of almost any conventional surface-to-air missile. If a terrorist wanted to shoot down a passenger jet flying out of Kennedy Airport that night, he would have positioned himself much further to the west -- where outbound aircraft from JFK weren't flying so high.
2. Related to #1, Flight 800 was flying several thousand feet lower than usual that night -- to make way for a northbound United Airways flight to Providence, Rhode Island that was running behind schedule. This was a turn of events that a terrorist could not possibly have foreseen -- if he had positioned himself at that location, he would have been firing under "normal" circumstances at a target that was several thousand feet higher than an altitude already at or beyond the edge of his missile's range.
so why were the two journalists tossed in jail for stealing into the fbi's hangar where the debris was being reassembled?