An improved flying prefab that I've been using on my helicopters for a very long time, but with a couple of minor improvements to the original one, and made it more "modular" so you can easily put it on any normal-sized avatar.
*Requires Unity 2018 (Unity 2018.4.20f1) and the latest VRChat SDK (VRCSDK2-2020.04.09.10.48 or later)
*Contains 1 example avatar scene file inside the "Flying Assets" folder.
~> To install, simply drag and drop the prefab onto your avatar, and provide the override needed. *An example avatar is provided.
~> Activate "Flying Mode" by clicking on it on the Emotes menu, and to fly, simply spam jump while moving. For VR users, you can access the triggers by holding the "thumbsup"/Shift+F8 (descend), and "fingerpoint"/Shift+F4 gesture ("Steep ascend"+JUMP = vertical ascent)