Bomb vs. Fire

This should be fun, figuring out exactly what material constitutes "incendiary" and which is "explosive" in the Detroit jetliner case. While we understand the different effects, I don't know how precise a distinction there is.

"A senior Department of Homeland Security official said that the materials Mr. Abdulmutallab had on him were “more incendiary than explosive,” and that he had tried to ignite them to cause a fire as the airliner was approaching Detroit."