While developing some in-plane software, we recently had to determine the best way to do end-to-end testing of our system. Unfortunately access to an actual plane was limited, and obviously both time consuming and costly. Fortunately we discovered the hugely extensible X-Plane. It provides a highly detailed flight environment (the scenery data requires 6 DVDs), and allows for easy writing of plugins to manipulate the environment, providing full access to all of the plane controls & environment. This allowed us to easily test our system on the desk, in a completely simulated environment, whilst still testing the entire system.