by someguy » Thu May 07, 2015 4:02 pm
Unfortunately, you have the perfect storm of an app and OS that aren't compatible, plus a computer that's too weak to run the app properly. For FG versions earlier than 3.4 to work under Yosemite, you have to launch FG from the command line, because the old Launcher requires an OS library that no longer exists in OS X 10.10.
FG 3.4.1 (the latest version) really wants more than 4GB of RAM and better video than Intel onboard. It should run, poorly, if you reduce the visual effects to minimum, don't use graphically-heavy planes like the 777 or C172P, and stay away from KSFO or other complex scenery. Multiplayer won't be any fun if it exposes you to other users flying fat airliners.
Or you could give up and buy a high-end iMac, like I did. Or pick up a used PC, buy RAM and a 2 GB video card, and use it only for FG.