1. A computer implemented method of managing airspace through which a plurality of aircraft are flying, comprising: obtaining user-preferred aircraft intent data of the aircraft that describe unambiguously the user-preferred trajectories of the aircraft through the airspace; obtaining time constraints for at least some of the aircraft, each time constraint comprising a user-preferred time of arrival at a common location; calculating the corresponding user-preferred trajectories from the user-preferred aircraft intent data; calling an initial conflict detection procedure comprising comparing the calculated user-preferred trajectories to identify one or more conflicts between user-preferred trajectories, and identifying the conflicted aircraft predicted to fly the conflicting trajectories; calling an initial conflict resolution procedure comprising revising the user-preferred aircraft intent data of one or more conflicted aircraft to produce revised trajectories in a way that is configured to achieve a primary objective of resolving conflicts and in a way that is configured to achieve a secondary objective of meeting the time constraints; and transmitting to the conflicted aircraft subject to revised trajectories the one or more revised aircraft intents.