Court of Justice cases like Territorial and Maritime Dispute (Nicaragua v. Colombia), Maritime Delimitation in the Black Sea case, Canada–France Maritime Boundary Case where court had used equitable approach and limited the continental shelves of islands. Tensions over the continental shelf were particularly high during the mid-1970s and again the late 1980s, when it was believed that the Aegean Sea might hold rich oil reserves. Turkey at that time conducted exploratory oceanographic research missions in parts of the disputed area. These were perceived as a dangerous provocation by Greece, which led to a buildup of mutual military threats in 1976 and again in 1987. Flight information regions Unlike the issues described so far, the question of flight information regions (FIR) does not affect the two states' sovereignty rights in the narrow sense. A FIR is a zone of responsibility assigned to a state within the framework of the International Civil Aviation Organization (ICAO). It relates to the responsibility for regulating civil aviation. A FIR may stretch beyond the national airspace of a country, i.e. over areas of high seas, or in some cases even over the airspace of another country. It does not give the responsible state the right to prohibit flights by foreign aircraft; however, foreign aircraft are obliged to submit flight plans to the authorities administrating the FIR. Two separate disputes have arisen over flight control in the Aegean: the issue of a unilaterally proposed revision of the FIR demarcation, and the question of what rights and obligations arise from the FIR with respect to military as opposed to civil flights. Demarcation By virtue of an agreement signed in 1952, the whole airspace over the Aegean, up to the boundary of the national airspace of Turkey, has been assigned to Athens FIR, administered by Greece. Shortly after the Cyprus crisis of 1974, Turkey unilaterally attempted to change this arrangement, issuing a notice to airmen (NOTAM) stating that it would take over the administration of the eastern half of the Aegean airspace, including the national airspace of the Greek islands in that area. Greece responded with a declaration rejecting this move, and declaring the disputed zone unsafe for aviation due to the conflicting claims to authority. This led to some disruption in civil aviation in the area. Turkey later changed its stance, and since 1980 has returned to recognizing Athens FIR in its original demarcation. In practice, the FIR