Once air routes have been planned, the next step is to match the flights with the available capacity. This is an important step as only a certain number of flights can be safely handled at any one time by each air traffic controller.
Each aircraft, using air traffic control files a flight plan and sends it to a central repository. All flight plans for flights into, out of and around Europe are analysed and processed, against the available capacity, in order to make the best use of airspace slots. This is done by air traffic flow and capacity management.