Much research has been driven by efforts to save jet fuel. Having more than doubled in price in recent years, it now accounts for about half of airlines' operating costs.
为节省飞机燃油人们已做了大量研究，油价近年来增长近两倍多，如今它几乎占了航空运营成本的一半。
2
Such trains can be driven by jet engines.
这样的火车可以用喷气发动机驱动。
3
Any of various winged vehicles capable of flight, generally heavier than air and driven by jet engines or propellers.