the 2010 Icelandic volcano eruption), overcrowding (as was happening in 2019), as well as collapses in air travel demand (as happened due to the COVID-19 pandemic in 2020). Management cost reduction and job creation: The SES would require far fewer air traffic controllers, who have high salaries, thus substantially cutting personnel costs by about 50%; the number of control centres might be reduced from about 60 to about 20. Meanwhile, the development of Single European Sky ATM Research (SESAR) technology could create 328,000 jobs across Europe. By comparison, the 27 member states systems employed a little under 58,000 workers (including 16,900 air traffic controllers) in 2010. Innovative coordination: The SES would stimulate coordination on innovation in areas such as sustainability. Formation flying: The SES would enable formation flying, including Airbus' fello'fly project, which will save energy and benefit from an updraft. Disadvantages ATC job losses: The SES would threaten the jobs of many air traffic controllers, because fewer would be needed to manage a pan-European sky. Security and sovereignty: Some EU member states, mostly larger ones, have expressed certain objections to relinquishing their current systems, primarily relating to national security and sovereignty concerns. For example, the SES could create problems concerning territorial sovereignty, such as over Gibraltar; Brexit seems to have removed this problem, however (see below). History Origins (1999–2004) After the Prodi Commission took office in September 1999, Transport Commissioner Loyola de Palacio launched efforts to structurally reform air traffic management across Europe, as she and many others had concluded that Eurocontrol was incapable of effectively carrying out its duties, particularly its decision-making and its failure to implement agreements. By the end of 1999, the European Commission had obtained the consent of all EU Transport Ministers for the 'creation of a single European sky', encompassing structural ATM integration and reform, and established a high level group of senior civil and military air traffic authorities representing the member states to prepare concrete policy proposals. After the high level group had completed its report in late 2000, the Commission used its recommendations to develop legislative proposals for regulating the SES. In October 2001, the European Commission adopted proposals for a Single European Sky, to create a Union regulator for air traffic management within the countries forming the European Union, Norway and Switzerland. The European Union regulator was supposed to merge upper European airspaces, currently divided into national zones. It was proposed