Next time you go through Security at the airport, you will have a better understanding as to why they ask you to take your shoes off.

This is what about 200 grams of Semtex (Combloc C4) will do to a pressurized 747
(9 PSI to simulate 30,000 foot elevation).  That's about 6.5 ounces  (enough to fill the spaces around a pair of feet in shoes).  While we regard the "Shoe Bomber" as a joke, if he'd been successful, no one would be laughing today.