A method for the determining, on board an aircraft, of an identifier of a communications centre with which an aircraft crew wishes to enter into contact, includes the following operations: a) the writing, by the crew, of a radio-communications frequency to a display unit of the cockpit of the aircraft, b) the determining of surroundings of the aircraft, c) the determining of the communications centers situated in these surroundings, d) the comparing of the frequencies of these communications centers with the frequency displayed on the display unit of the cockpit, and f) when the frequency of a communications centre is identical to the displayed frequency, the display on the aircraft display unit of the identifier of said communications centre having a frequency identical to the displayed frequency.