Propanes Expensive and many people have families and cant afford the stuff, so they steal it because they cant get assistance because they were drug
abusers.
Terrorists aren't going to use that type of propellant...Too big and heavy
Whiteman Air Force Base is where the B2 Stealth Bombers are based. At about $1
Billion each, and only 20 available, they would be a nice target for terrorists.
Whiteman also has a squadron that flies some of the drones used on the M.E. Seems like a good way to reduce the US ability to monitor Daesh
activity.
With respect to propane tank explosions, I remember that Myth Busters did an episode about that. Might be worthwhile to take a look if anyone is
interested enough.