Actually in the pre-crisis era (before 1987), Wonder Woman could not fly, so she used the invisible jet. After that, in post-crisis (after 1987), she went through some adjustments, and the jet was discharged and she got the ability to fly, as a gift of the god Hermes. After the 2011 reboot (the news 52), Diana has gained new powers. As the natural born daughter of Hippolyta and Zeus, she has inherited some of her father's powers, which is suppressed by wearing her bracers, and now she can't fly. We are in the "original state".