The European Geostationary Navigation Overlay Service (EGNOS) is the first pan-European satellite navigation system. It augments the US GPS satellite navigation system and makes it suitable for safety critical applications such as flying aircraft. The EGNOS Safety of Live service has been officially declared available for aviation on 02 March 2011. Space-based navigation signals have become usable for the safety-critical task of guiding aircraft – vertically as well as horizontally – during landing approaches.