From the start Google Earth has been fascinating in its own right. But since its introduction about two years ago, it has been additionally interesting as a "development platform" -- a layman's glimpse at the sophisticated world of "geographic information systems," which are essentially ways of mapping complex data onto a real, visible map. (More info here. Subscribers only.)
The latest and in a way most surprising application to be laid on top of Google Earth is its new, semi-hidden flight simulator. You call it up with Ctl-Alt-A in Windows systems, and Cmd-Opt-A on the Mac. If that doesn't bring up the simulator, you don't have the current release of Google Earth. which you can find here. I haven't played with it enough to know whether it matches the best real flight sims, from Microsoft and X-Plane. Also, any flight simulator, IMHO, requires a joystick rather than control-key operation to be any good. But that it exists at all is interesting, and its connection to the worldwide terrain coverage of Google Earth is a plus.
Nice touch: the two aircraft it offers are the Air Force's F-16, its design influenced by John Boyd and his "fighter mafia" allies; and Cirrus Design's SR-22, its design determined by the Klapmeier brothers and their colleagues in Duluth. More info about the flight sim, which has already been extensively publicized in tech blogs, here and here.