Flight-testing at Toulouse, France, and Frankfurt, Germany, has proved that a reliable alternative to an ILS signal can be produced with a GNSS constellation and single-frequency input signal. Eurocontrol’s Sesar air traffic management research team worked with equipment manufacturers Thales, Indra-Navia, Honeywell and Thales Avionics using a ground-based augmentation system (GBAS). Further testing at both airports is expected to resume in the middle of next year.