How to get the THX helicopter mod without needing minecraft.jar in finder?

I might have accidentally deleted minecraft.jar in ~/Library/Application Support/minecraft and I need it to download thx helicopter mod. How can I still download THX helicopter mod without minecraft.jar?

You don't need that file anymore – it's a leftover from version 1.5.x, and since then the equivalent file (which contains most of the actual game) is stored in the versions folders, one for each version of the game you've installed with the new launcher. You don't need minecraft.jar anymore, and can't install mods using it anymore anyway since the game doesn't even use it anymore.

So some digging turns up this THX Helicopter mod. It's not available for the current version of Minecraft – the latest it supports is 1.6.1 – and requires Forge (or ModLoader, but who uses that anymore).

Fortunately, the normal Forge install instructions will get you 99% of the way to having this mod installed. Then just drop the mod's zipfile (make sure it's the 1.6.1 version) into the folder the Forge instructions tell you to put mods in, then play (again, using the launcher profile the Forge install instructions tell you to use).