So in the current economic climate with European air traffic 13% below it's 2007 levels Europe's controllers suddenly can't handle it any more. Yes aircraft change speed, level, heading and departure times for any number of reasons, this is not a utopian world and forcing aircraft to burn thousands of tons of extra fuel to save understaffed atc units a few pennies is a sad reflection on (mis)management culture. The cry of flight safety is hackneyed and wearing a bit thin. Provide the service for which the airlines pay hundreds of millions in Eurocontrol charges.