Flying Foxes and Fearsome Ferals

The name "Flying Fox" was used on three worlds, there was the Flying Fox of Earth-One who was a young Bruce Wayne and would later become that world's Batman. The Flying Fox of Earth-Two was a frequent foe of sky criminal Air Pirate A-X. The Flying Fox of the Post Crisis Earth seems to have originated on Earth-8 previously.

Radiologist/pilot Lou Rex Darrell was a flying detective in the image of his world's Batman, similar to his younger counterpart, zoologist aerialist Kirk Langstrom, who also was an investigator with the ability to defy gravity. 

Kirk studied the nocturnal gliders that the Dark Knight was modeled after, and developed a bat extract. With this chemical compound, he became the eerie Man-Bat of Earth-One. Rex built a state-of-the-art aircraft to aid him in his costumed crusade by gliding through the skies on his vehicle.

While Flying Fox did not become a human-animal hybrid like Man-Bat, his mechanical aptitude allowed him to defy gravity in a much more powerful external frame through his specialized plane, with somewhat similar effects to Man-Bat's biological research had done to himself.

 

After initially consuming his bat extract, Langstrom temporarily turned insane and became a recurrent foe of Batman, before his hero turned adversary found a way to reverse  the process and return Kirk to his human state. For a time, as Man-Bat he was a protector of New York City. Unfortunately, madness would once more consume him reverting him to an enemy of Batman.

Likewise, after a few notable tales as a good guy during the early days of World War II, a debilitating head inury during the war left Darrell with a greedy rather than good mental disposition. Under the cover of his career as a radiologist, the former Flying Fox attempted to steal valuable radium which led to conflict with Batman and Robin (Batman #37). Of note is his preference for green and brown clothes from his Flying Fox days 

Although seriously injuring the Dark Knight Detective, Darrell was revealed by Batman from an x-ray image as the criminal's true identity, and brought to justice.

There were other creatures on their respective worlds. On Earth-One, there was Andrew Bennett, Lady Viper, Anthony Lupus and Gregori Arcane who each mirrored Earth-Two's Creature Commandos in Vincent Velcro, Myrna Rhodes, Warren Griffith and Elliott Taylor.

While the former quartet each interacted with the Batman on their Earth, there is no documented occurrence of the later foursome having met their own Batman, since they operated primarily in Europe during World War II before they were jettisoned into space accidentally on a last mission.