Baltic Air Policing is a NATO mission that began in 2004 when the three Baltic countries, Estonia, Latvia and Lithuania joined NATO. These countries receive the Policing Action because they don’t have the required air capabilities. Some NATO members rotate flying over these countries to protect the airspace from intrusions by Russia, especially since the 2014 Russian invasion of Crimea. Missions last four months before another air force assumes the duties. The Baltic Air-Policing mission is purely defensive.