urope is experiencing air traffic congestion, leading to significant delays, increased costs and CO2 emissions. This is partly a result of the fragmentation of airspace and of the air traffic control process. There is considerable room for improvement. For 10 million flights a year, it is estimated that the actual route flown is 5% longer than ideal. For some routes, such as Amsterdam-Zürich, it is even 20%. The annual cost of fragmented European skies is estimated at 3.4 billion euros.