GSINTA - GNSS Signal-in-Space (SiS) Integrity Assurance project is addressing the underestimated and hazardous effects of external EM interference signals on GNSS SiS integrity, in safety critical air navigation applications. The project timely supports safety assessment considerations during actual global transition to GNSS as a primary mean of airspace navigation. The objectives of the research project proposed, focused on active mitigation of interference effects on GNSS SiS integrity, presents innovative approach in the field where similar researches do not exist at the moment.Continuous airborne monitoring of GNSS SiS and detection of interference signals, continuous calculation of SiS integrity with regard to external interference signals and their isolation from solution during critical phases of airspace navigation applications, as concept do not exist at the moment.Scientific contribution is considered to be in development of the new navigation algorithms and their fully operational validation in critical airspace navigation applications, with prospect to be used in other Safety of Life (SoL) applications.Scientific and technological reasons for carrying out such research in the field, is absence of well established methodology for in flight SiS integrity calculation with regard to external interference signals and generic approach of interference mitigation for all GNSS in use over European area.Supporting basis for the research proposed are recent findings of the ground based interference measurements (opposed to the airborne one proposed), conducted by one of the European entities in the field, which have revealed the GNSS SiS vulnerability higher than predisted in airspace navigation applications, placing it in its reports as critical to the safety of navigation and plans for airborne system developmet are announced.