Something seriously distorted here:
."AFP officers interviewed a young teenager who identified the suspect item as a homemade firecracker that he was carrying in his luggage on the flight from Maroochydore to Sydney"
"thermite, a flammable compound used in some types of grenades"
AFAIK, Thermite, mixture of Fe***and Al***, difficult to ignite, used for incendiary devices (bombs yes, grenades? maybe WP) and welding. While it burns quite well when ignited and can be described as being like a volcano I have some problem with the firecracker idea.
Maybe the assorted experts (including the "young teenager") didn't have a clue. Now when I was a young teenager.....