Good one, though I do have to wonder as to why a character who's got the ability to fly also has a jet.
originally she wasn't able to fly, and used the jet to get around. much like the early superman comics, she could jump very high though and fall safely from great heights. (she was originally just a super-athlete with the lasso and bulletproof bracers) more recent comics have given her flight (since the jet was kinda silly) but the jet keeps rearing its head anyway.
like most of the older DC heroes, her original version saw a lot of changes during the 'golden age', as writers would append new powers or abilities to the characters in order to make stories more diverse in an age of the comics code (when what was allowed storywise by the company executives was heavily controlled and fairly simplistic)
that was one of the reasons DC did the crisis on infinite earths.. when the stories were allowed to become more complex, trying to stay in continuity with the older stuff (and all the 'alternate earths' that failing to do so forced them to invent to explain it) that they decided to clean house and reboot.. but decided it would be better to make an event out of it all so readers wouldn't be as confused.
it didn't help really, in the long term (the continuity problems continued to happen) but it made for entertaining reading.