There is greater emphasis by terrorists on inflicting heavy casualties. And the terrorist threat in the 1990s also emanates from sources that are more numerous, and more varied, than was true of most past eras. So there is still plenty of work for intelligence to do. Chiefly in the following four ways, which are in increasing order of specificity. Gauging the terrorist threat to aviation .
Intelligence helps to assess the overall magnitude of the terrorist threat to civil aviation.
It is thus one input to decisions on how much to spend on security countermeasures. Some of the information needed to gauge the seriousness of the threat is openly available and does not need to come from intelligence agencies. The past history of terrorist attacks on aviation, and trends in terrorists' choice of aviation versus other targets for actual attacks, are matters of public record. Intelligence sometimes provides other indications, however, of terrorist interest in aviation as a potential target. Terrorist modi operandi .