Helderberg was not just a 747 carrying military equipment, it was a passenger flight with a secret (and still undisclosed) military cargo, widely believed to have been rocket fuel in the hold. The embarrasing coverup continues despite many official enquiries.
Helderberg is believed to have been carrying "Ammonium Perchlorate" (simply known as "AP" to solid rocket types). AP is not rocket fuel as such, but it is a commonly used oxidizer in solid rocket fuel (the Space Shuttle SRB's were AP based). While AP is not particularly flammable, it is a powerful oxidizer - once it does start burning it's nearly impossible to extinguish until the source of the PA is exhausted.
If it was in fact the case that Helderberg was carrying AP, those responsible should have spent their lives in prison for manslaughter
