fe ailford used rdx, a white powder. he filled three-quarters with the concoction and the rest with toothpaste. it smells and tastes like toothpaste. i have presented this in such a way that somebody giving it a casual inspection will probably pass it. reporter: the size of the container that alford used is the size you place in checked baggage, but two smaller containers this size, which traditionally you can carry onto a plain, can also be used. these tubes would have to be either attached or placed near each other to create a similar explosion as the one you just saw. they can be detonated by a heat source. erin? all right. when we talk about the heat source, this is not just some sort of a hypothetical, right, that they said they re going to do this and authorities are worried. a toothpaste bomb has been used on passenger jet before. reporter: it has. in october 1976, anti-castro cuban operatives hid explosives