1. A computer implemented method for constructing a flight trajectory of an aircraft, deployed in a flight management system, said flight management system configured to determine, on the basis of a flight plan advised by the pilot, an objective navigation point sequence (SPNO), an objective navigation point being characterized at least by a geographical position, and configured to determine a flight domain (D v ) consisting of a set of parameters defining an aerodynamic behaviour of the aircraft, said flight trajectory being defined as a sequence of state vectors, the method comprising two successive steps: first computing, with the flight management system, state vectors representing the trajectory of the aircraft; the state vectors having as components at least a time (t i ), a geographical position (X i ,) of the aircraft and components of a speed vector (V i ) of the aircraft; a state vector (E i+1 ) being determined on a basis of the preceding state vector (E i ) preceding it in a sequence by: computing the components of a following speed vector (V i+1 ), including: determining a flight setpoint, by selecting an objective navigation point from the objective navigation point sequence (S PNO ), then determining a joining strategy adapted to the flight setpoint and to the flight domain (D v ) by means of a predefined library (L sr ) of joining strategies, then determining a manoeuvre by means of the flight domain (D v ), allowing the aircraft to follow the joining strategy towards the flight setpoint, and second computing, with the flight management system, other components of the state vector (E i+1 ), on a basis of the components of the following speed vector (V i+1 ) and components of the preceding state vector (E i ) in the sequence proceeding it in the sequence.