Oh I wouldn't discount the few home grown idiots who somehow think a 10/20 lb payload of homemade explosives is going to make some sort of statement. The true terrorists are only interested in large significant targets requiring big payloads for emphasis. Now a full size 172 could carry how much? A cube van how much? Now a fully indoctrinated terrorist is willing to die for the cause so no need for remote detonation. So if you were a terrorist which would you think has the greatest chance of success?