Additional systems are designed to ensure the reliability of the data. Their work is not based on satellite signals, and they can be used to verify the correctness of information. For example, Airbus mentioned this cross-validation in its concept
. It will be appropriate to say that for satellite ADS-B in Europe, the multilateration-based systems act as a "reserve layer". In the EU it is noted
that these systems are deployed jointly more often. The coordinates of the aircraft are determined by the time delay of receiving a signal from the aircraft by a network of ground stations, in the case of multilateration. The satellite system, which signal can be blocked, is not used.