This paper presents the technical details of Tiriba, which is a small autonomous electrical airplane used into pre-defined missions and applications such as agricultural and environmental monitoring. This class of aircrafts has taken advantage of the miniaturization of electronic components and modules such as GPS receivers, digital cameras, wireless communication equipment, and other sensors. One of the main components of Tiriba is the autopilot module, which is capable to control the aircraft and keep it in a predefined route. This paper addresses the use of model driven development of the system and its multiprocessor platform to support the four components that compose the UAV control software architecture.