1. Aircraft piloting aid system, with GNSS-IRS hybridation, designed for onboard installation in an aircraft, comprising an inertial reference system IRS with at least two inertial reference units, each supplying a set of inertial data and at least a first multimode receiver supplying a first set of guidance signals and a first set of augmented GNSS data a second multimode receiver supplying a second set of guidance signals and a second set of augmented GNSS data, each receiver including two digital processing boards with a mutual checking function for the data generated by each of said digital processing boards to supply said set of guidance signals, and a single augmented GNSS signal processing board, supplying said respective set of augmented GNSS data, wherein a function for generating guidance data from the GNSS data and the inertial data with integrated fault detection is distributed on said inertial reference units and said digital processing boards of said multimode receivers.