Google Earth 4.2 came with a handy Easter egg: a hidden flight simulator. You could fly your virtual plane from different airports or launch it from anywhere in the sky. The feature was so popular that it was included as a standard feature in Google Earth and Google Earth Pro. No unlocking required.
How to Use Google Earth Flight Simulator: Tutorial
The graphics are realistic and the controls are sensitive enough to feel like you have a lot of control. If your plane crashes, Google Earth asks you if you want to exit Flight Simulator or resume your flight.
See Google's instructions for using the virtual plane. There are separate instructions if you are using a joystick instead of a mouse and keyboard.
Once Google Earth is installed, follow these instructions to activate Flight Simulator: