PX4 autopilot

PX4 autopilot is an open-source autopilot system oriented toward inexpensive autonomous aircraft.
Low cost and availability enable hobbyist use in small remotely piloted aircraft. The project started in 2009 and is being further developed and used at Computer Vision and Geometry Lab of ETH Zurich (Swiss Federal Institute of Technology) and supported by the Autonomous Systems Lab and the Automatic Control Laboratory. Several vendors are currently producing PX4 autopilots and accessories.
Overview.
An autopilot allows a remotely piloted aircraft to be flown out of sight. All hardware and software is open-source and freely available to anyone under a BSD license. Free software autopilots provide more flexible hardware and software. Users can modify the autopilot based on their own special requirements.
The open-source software suite contains everything to let airborne system fly including
Other open-source robotics projects similar to PX4 include:
Supported hardware.
List of autopilot hardware supported by PX4 autopilot flight stack. 