Aerial surveillance by foreign powers
Over-flying by foreign aircraft
Independent international air surveillance
The air space above countries is theoretically controlled by that country, but not in all instances or above certain heights.
In hopes of forging trust between superpower nations, US President Dwight Eisenhower promoted the notion of "open skies" for foreign aircraft in 1955. Cold War suspicions nullified Eisenhower's attempts until 1989, when US President George Bush attempted an open skies revival.
Over-flying by reconnaissance aircraft builds confidence by allowing each side in a dispute to check that the other is honouring its treaty obligations, especially in relation to military activity.