When I think of a jet, I think of the engines - which aren't installed on airplanes only, as I see them fairly often on mecha.
Also, there's the various mecha musume and all the Strike Witches pics.
Posted under General
I wasn't really sure on this, though there are plenty of mecha musume and personifications even amongst the airplane tag. Beyond the mecha musume and personifications, there really wasn't much else besides planes. One of the few that was tagged jet, but not a mecha musume or personification was post #236388, but I think it'd be better under a different tag, perhaps jetpack.
For the majority of Strike Witches, they won't fall under jet, since the majority of depicted striker units have propellers. Also it'd be better to tag them with the striker_unit tag, then tag them with airplane or jet, or whatnot.