"a few thousand tons" of jet fuel is a LOT of jet fuel! More than two aircraft can carry I suspect!!!.. But the point is that it needs to burn at a high enough temperature to melt steel.
In regards to bushfires... aluminium melts at a lot lower temperature but I've only seen burnt out (steel) car shells.
A plane load of jet fuel melting or cutting a steel structure such as the WTC buildings fails a sanity test in my view but either way I don't know how steel could remain molten for six weeks (fwiw arc welds solidify in a matter of seconds when fabricating steel structures).
It may just be that the reports are of solidified metal pools in the WTC wreckage but that is not the information that I've seen presented.
