I didn't know where to put it so if it's in the wrong category feel free to move it.
And hope this is not considered spamming :-/
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There are quite a few other great freeware & open source Plane, Car & Ship simulators. There are also some that simulate all the above
Here are just a few.
Car/Racing
Dolphinity Racer
An Open source game that focuses on realism, graphics & simplicity to create your own addons. In that order.
Lamborghini Murcielago roadster cruising Down the countryside.
It starts with one car and one track but there are plenty more. Does your copy of Forza motorsport or Need for speed shift have a car that you would like to see in the game? Convert it for yourself.
Pros