They ultimately purchase jet fuel. Jet fuel has no futures market but since the biggest price component is crude oil, it follows crude oil pricing.
By trading crude oil futures they have protected themselves in a rising price market.
Recently Rio Tinto increased its iron ore prices by up to 97%. Iron ore is not traded on the futures market and demand did not jump 97% in a few weeks so what would account for the increases in price? Can we say the company
its self is speculating? Betting that future demand will continue or accelerate? China, Japan, Korea are willing to accept price increases of 85, 95 and 97% for iron ore because they see future demand going up.
In the same way speculators are trying to guess future markets.
A good article on the futures market is at the Mises.org site, “The Market Works Just In Time”, by Robert P. Murphy.
As a consequence of iron ore prices going up the price of scrap steel will continue to go up too since a lot of scrap is used in making steel.