I ran the numbers this morning. My understanding is that the Lockerbie bomb consisted of between 300 and 400 grams of Semtex, which translates to something between .65 and .9 pounds.

HMX and RDX are both compounds used in making plastic explosives like semtex.

http://www.kansascity.com/mld/kansascity/news/politics/10010371.htm?1c

The thing is that depending upon the flavor of semtex being manufactured, the amount of HMX or RDX can vary between 50 and 90 percent of the actual semtex weight.

(No, I am not a weapons expert, but I did google this and feel reasonably comfortable with my sources).

So in reality, 380 tons of this stuff should be more than sufficient to create over one million Lockerbie bombings.

As you say, this is enough to down every airliner tens of times over.

Now, arguably, one might wonder what Saddam was doing with all this stuff. I'd argue that any modern military is gonna have a lot of plastic explosives laying around. Untold tons of this stuff is stockpiled underground in Kingsport, Tennessee, by the US Army. Just to name one of our nation's plastic explosives stockpiles.