I have a macbook pro running 10.4 tiger, and I have flightgear 0.9.9. About half of the planes I have downloaded dont work. The errors in my console are something like this:---747 i think---fgfs(2143,0xa000ed58) malloc: *** Deallocation of a pointer not malloced: 0x1a8cde00; This could be a double free(), or free() called with the middle of an allocated block; Try setting environment variable MallocHelp to see tools to help debugFlightGear Exited.Aug 18 18:31:15 sams-computer crashdump[2146]: fgfs crashedor ---A320---RenderTexture::BeginCapture(): Texture is not initialized![31mYOU HAVE AN INCOMPATIBLE CFG FILE FOR THIS AIRCRAFT. RESULTS WILL BE UNPREDICTABLE !!Current version needed is: 1.65 You have version: [39mFlightGear abortingFlightGear Exited.

I think many of the aircraft that you can download are only compatible with v9.10. And unfortunately, FG 9.10 hasn't been built for Mac because the project lacks a Mac developer.