People don't hijack planes anymore because that old system...

People don't hijack planes anymore because that old system of hijacking in order to barter for a prison release or get to a different country no longer works, exactly, because 9/11 recoded the hostage's interpretation of a hijack. If a hijacker isn't trying to use the plane as a missile, then he is in danger of being killed by the hostages. There is no minor terror threat anymore. No mid-level terrorism.