A method for authorizing the flight of an aircraft provided with a hybrid power plant having at least one heat engine and at least one electric motor electrically connected to an electrical energy source comprising several electrical accumulators. The method comprises extracting (STP1), while on the ground, an electrical energy or an electrical power to be extracted from the electrical energy source during a predetermined time period and determining (STP2) for the electrical accumulators, respective initial values of an operating parameter, calculating (STP3) an average value from the initial values, determining (STP4) a minimum value from the measured initial values, issuing an authorization when a difference between the average value and the minimum value is less than a threshold and a prohibition when said difference between the average value and the minimum value is greater than or equal to the threshold.