A method for selecting radionavigation beacons using an onboard navigation system aboard an aircraft from a list of eligible beacons, includes a step for formulating a criterion for selecting a pair of beacons (B.sub.X, B.sub.Y) from among beacons forming part of a list of eligible beacons, and the selection criterion is based on a search for a maximum duration of membership, for instants subsequent to the instant t.sub.1, for which the 2D terrestrial position of the aircraft belongs to the zones of employment of all the pairs of beacons achievable from among the eligible beacons, on the basis of a given predictive trajectory of the aircraft.