The X-Plane Communications Toolbox (XPC) is an open source research tool used to interact with the commercial flight simulator software X-Plane. XPC allows users to control aircraft and receive state information from aircraft simulated in X-Plane using functions written in C or MATLAB in real time over the network. This research tool has been used to visualize flight paths, test control algorithms, simulate an active airspace, or generate out-the-window visuals for in-house flight simulation software.