JUST HOW EXPLOSIVE ARE THEY? Much has been made of the fact, by opponents of the administration, that the missing explosives are so powerful that only a pound (or half a pound, depending on the source) was capable of taking down Pan Am Flight 103.

I’m under the impression, however, that an airplane requires very little explosive to take it down, because it’s just a thin aluminum skin covering a) a lot of very important wires and b) the open sky, so a little of it is likely to either damage the plane beyond operability, or catastrophically depressurize the plane. Can readers enlighten me?

Update Bill at INDC points to a Baltimore Sun piece which says that the missing explosives are only “slightly more powerful than TNT”. He also points out that it was neither HDX nor RDX, but the much more powerful Semtex (of which RDX is a component) that brought down Pan Am 103. The last points out that the explain did explode into multiple pieces when the bomb went off, so the explosion must have been very powerful.

Further Update Another reader writes

The bomb used in the downing of PA-103 was not very powerful, just powerful enough.

I’ve seen the wreckage of the plane as assembled at the UK’s equivalent of the NTSB. Most of that wreckage is in large pieces. What brought the plane down was that the integrity of the plane’s skin was broken. With even a square-foot’s worth of skin torn open into a 500+ mph wind stream, the plane had to come apart.

There’s a strip of aluminum skin, originating at the place where the explosion breached the hull that “unzipped” up and over the top of the plane, then down the other side, all the way to the bottom of the hull. The hole created by the explosion is no bigger than a softball. The strip of skin that “unzipped” ranges from six inches to 10 feet in width; the entire strip is over 60 feet long.

Once the integrity of the hull was breached, though, that wind simply tore the plane apart. The NTSB website also has good details on the physical aspects of the explosion.