Flying fox are aggressive, especially if you are used to SAE.
They are especially aggressive toward their own species, and similar looking fish (so do not put SAE in the same tank).
They can be somewhat aggressive to similar shaped fish like many of their relatives with the common name '...Shark...' like Red Tailed Shark, Rainbow Shark and so on.
They are not usually too aggressive to other species that are different shaped, but compared to SAE they are more pushy. Make sure there is plenty of room in the tank. Do not try to keep one in a 10 or 20 gallon, for example, and plenty of plants will help break up the line of site. Mine was not interested in a cave, but more of a mid-tank fish.