Few creators of simulator games allow free distribution of the source code of their creations. This means that the utility is open to amendments that allow successive improvements in the product itself.
This is the case of Flightgear, which consists of a flight simulator and is totally free.
Flightgear has a truly enviable graphical interface with a high-definition in terms of prototype and scenarios.
With regard to its operation, it is necessary to say that, being a flight simulator it seeks maximum reality, it is understandable that it is somewhat difficult to manipulate. With the passage time the user gets used to handling it.
In short, Flightgear features a virtual flight with high realism that will be improved further in their new versions, thanks to it being open source.
-- Microprocessor: 800 Mhz or higher.
-- Video Card: one compatible with OpenGL.