If this was indeed caused by an explosive device it was definitely no shoe or underpants bomb. Anyone with the capability to smuggle a real bomb on board and detonate it in flight, would not be traveling on a 2 year old stolen passport.
On three occasions I've filmed the detonation of 500ml of home made liquid terror in an airframe, these were demonstrations on unpressurized hulls which were not traveling at 500mph.
Was a "liquid ban" in force at the first security point on this flight?