ONESKY is a preparatory, accompanying and support measure of the European Commission (DG TREN) in the 5th Framework Programme GROWTH, Sub-programme Area: Traffic management systems. Up till 2000, there has been a sharp and steady rise in delays to aircraft. This had major repercussions for users and placed a substantial financial burden on airlines. The delays were caused in particular by the air traffic control system, which appeared to be less and less capable of handling the phenomenal growth in air travel.

In 2001, one flight in four was delayed due to air traffic problems. Despite a temporary slowdown following the attacks on 11 September, estimates are that air traffic will grow by 4% a year over the next 15 years. Delays cost airlines between EUR 1.3 and EUR 1.9 billion a year. While there has been a constant increase in air traffic control capacity in Europe since 1990, it is now trailing three years behind the growth in air traffic. The technical improvements made by Eurocontrol, the international organisation for the safety of air navigation, have not been enough to reverse the trend and delays continue, in particular, in the more central areas of the European Union of 15 Member States.

Airspace is in fact still basically organised as it was in the 1960s. Each country regulates its airspace without regard to cross-border traffic flows: a flight from Rome to Brussels passes through nine different control centres. The Single European Sky is an ambitious initiative to reform the outdated architecture of European air traffic control. It comes at a time when improved air traffic and aircraft positioning and communication technologies, such as Galileo, offer opportunities for significant improvements in the efficiency and safety of air travel. It responds to the need to conceive developments in air traffic management as a building block of the Community transport policy, enshrined in the White Paper of 27 November 2001.