Dick, actually all you would need to do would be to punch a hole in the thin aluminium skin of the plane. The pressure inside the cabin while the plane is at 30-40 thousand feet is immense. One tiny little hole and the pressure inside the cabin would finish the plane. Add that to the fact it would be over the ocean with virtually no chance to discover where the explosive was or what type it was and the plan is pretty ingenious.
What I don't get is that if you can blow a plane up with the contents in the cabin, what is to keep you from mixing the ingredients up before hand, stowing them in your checked baggage, and then detonating the thing when you are over the ocean. Do they think the terrorists are really that stupid not to figure that one little issue out?
Oh, well. If it was a real threat I hope they caught the perpetrators. Better to have all this debate than thousands of dead and missing loved ones.