Well, yes, Engines. But the determinants of range include fuel fraction, lift/drag ratio and engine SFC. So while the F-35B carries nearly 80% more internal fuel than the Harrier, it's also a lot heavier and (outside of hover mode) its engine has a lower bypass ratio. Also, unlike most aircraft with afterburners, it doesn't carry external fuel. It will be interesting to see what the range is like on the combat profiles that get used in service.
The larger point is that it's much easier to get range if you don't have to do high-g or supersonic. But then, you also have to look at how much supersonic/high-g is included in any given mission profile.
Last edited by LowObservable; 4th Oct 2018 at 13:14.