In recent years, Wireless Sensor Networks (WSN) have been considered for various aeronautical applications, including flight tests during the development of a new aircraft, and Structural Health Monitoring (SHM) during commercial exploitation. Up to now, these implementations use wires inducing a burden of kilometres of additional wiring (300 km on an Airbus A380 for specific sensing during flight test). However, going wireless for communication also requires being wireless for energy: isolated from the on-board electrical network, each sensor node needs to be self-powered. Environmental concerns, together with economical and safety-related issues, often prohibit the use of electrochemical batteries. Fortunately, energy may be harvested in the environment, providing a reliable and sustainable electrical power source… But is this story true? Considering the aircraft environment and the required test procedure for avionics, are technologies mature enough to provide low volume, low mass, reliable and efficient energy harvesting solutions? The purpose of this presentation is to answer this question through examples of hands-on tests in airliners [1] [2].