Futhermore, they can't even keep their stories straight. They have "explained" that what explosives they did find on the plane came from a "dog training exercise," a story with several significant holes in and of itself, even if it didn't flatly contradict the "zero evidence of explosives" story.
That story clearly fails the smell test ; however,there was a terrorist who was doing "tests" on mini-bombs in aircraft at about the same time. In one of his little "experiments", a mini- bomb he planted under a passenger's seat blasted some hapless, picked-at-random passenger into mush, and forced the emergency landing of the plane. He was using nitroglycerine (!!!) in his shoe bomb sized charges, but could have switched to something more stable.
Source: THE CELL by Miller, Stone, and Mitchell