The present disclosure provides a computer-implemented method of generating a description of aircraft intent expressed in a formal language that provides an unambiguous description of an aircraft's intended motion and configuration during a period of flight. A description of flight intent is parsed to provide instances of flight intent, each instance of flight intent spanning a flight segment. For each flight segment, an associated flight segment description is generated that comprises one or more instances of flight intent that describe the aircraft's motion in at least one degree of freedom of motion. Flight segment descriptions are compared with constraints and/or objectives and the associated flight segment descriptions are enriched with information describing relevant constraints and/or objectives. The enriched flight intent is converted into aircraft intent by ensuring that the flight segment descriptions close all degrees of freedom of the aircraft during the period of flight.