A method for displaying a flight plan having at least one waypoint on a flight display of a flight deck of an aircraft having known flight constraints, including receiving a user input for a user-inputted waypoint and generating an alternative waypoint when the user-inputted waypoint is not suitable and displaying same.

An electronic flight planning system is provided, arranged to implement a preferred method for identifying conflicts between flight plans for aircraft. In the preferred method, the system receives, as data input from one or more users, a plurality of flight plans each defining a flight by an aircraft; the system determines, for each aircraft and its respective received flight plan, a three- dimensional region of potential conflict, representative both of the uncertainty in the position of the aircraft and of a region of air exclusion appropriate for the aircraft or for the respective received flight plan; and the system determines, on the basis of the determined regions of potential conflict, whether one of the received flight plans is in conflict with any of the other received flight plans.

A method and system for determining a preferred flight path is disclosed. In one aspect, a processing system constructs a probabilistic roadmap search graph 360 including PRM nodes (362) and PRM edges (370). Each PRM node 362 includes a latitude/longitude pair (364) and an altitude (366). Each PRM edge (370) extends between two PRM nodes (362). Departure and destination nodes (380, 390) for take-off and landing weights (384, 394) are connected to the search graph (360) thereby generating costed climb and descent edges (386, 396) to reachable PRM nodes (362). The search graph (360) is searched by the processing system (100) to determine one or more of a cost minimised potential flight path between the locations (382, 392). A cost of traversed PRM edges (370) are calculated during the search. A potential flight path is selected using an objective function for outputting a preferred flight plan.