1. A method of automatic determination of a descent and approach profile for an aircraft, implemented on the basis of a flight management system based on one or more electronic computers, the descent and approach profile evolving from a start point DECEL of onset of the deceleration of the aircraft to a stabilization point, comprising a sequence of segments defined between successive characteristic points some of which are aerodynamic configuration change points, the configurations being taken from among a discrete set of predetermined aerodynamic configurations; the method of automatic determination being based on a backward computation for propagating a state of the aircraft along the segments of the sequence from the stabilization point to the start point DECEL of the onset of the deceleration of the aircraft; and the method of automatic determination comprising for each current segment S(i) covered in the profile, delimited between an associated current start characteristic point SP(i) of the backward computation and an associated current arrival characteristic point SP(i+1) of the backward computation, a step of determination of one or more next aerodynamic configurations C(j+1) of the aircraft on the basis of a current configuration C(j) active at the current start characteristic point SP(i) of the backward computation and of a nominal sequence of change of aerodynamic configurations; and a step of determination and provision for the next aerodynamic configuration or configurations (Cj+1) of a range of speeds of possible use of the said next aerodynamic configuration C(j+1), delimited by a minimum speed V min (j+1) and a maximum speed V max (j+1); the method of automatic determination comprising for each current segment covered S(i), a step of determination of an optimal speed V OPT (i) of the aircraft over the range of speeds of the next aerodynamic configuration C(j+1), the said optimal speed V OPT (i) of the aircraft being dependent on a predetermined deceleration strategy and/or on predetermined constraints inherent in the flight procedure or introduced by the pilot in his flight plan.