I'm prior service as well and we were trained in improvised munitions... ways of making ordinary things "go burn or boom". Smuggling basic components on to a plane is a trivial task. A little harder to build an effective bomb from components behind the TSA security screening but not impossible.
LOL The Army has a whole series of Field Manuals (FM) on improvised explosives - all of which are worth reading to avoid some of the more obvious ones.
I won't list the titles or names for obvious reasons - I refer to them collectively as "dead cat bomb books"
Bottom line as pointed out by Heinlein years ago
There are no dangerous weapons, only dangerous people!