Now can press A, D and S to fly left, right dand back. Also add an small blue box on the left of the screen to remind you that you are flying. Invincibility is not included. If you want the invincibility, you can find a small script under Misc.
This version will not make the player invincible at all. Other versions add invincibility to prevent possible death from the impactions while flying. But I never have such experience. So you can use this version with no problem.
This version will make the player invincible while the fly mod is activated. If you have another mod that change the invincibility, when you disable the fly mod, invinciblity enabled by other mod may be disabled.