X-Plane

X-Plane is the world's most comprehensive and powerful flight simulator for personal computers. With the most realistic flight model available for home users, X-Plane is not just a game - it is an engineering tool that can be (and is) used to predict the flight characteristics of nearly any aircraft with incredible accuracy.

Minimum system requirements: 

CPU: 2.0 GHz (x86-compatible)
RAM: 2048 MB
GPU: OpenGL-compatible with 128 MB VRAM