BARCAP

patrol of combat aircraft to prevent penetration of enemy aircraft into a particular airspace

Combat air patrol (CAP) is a type of flying mission for fighter aircraft. A combat air patrol is an aircraft patrol provided over an objective area, over the force protected, over the critical area of a combat zone, or over an air defense area, for the purpose of intercepting and destroying hostile aircraft before they reach their target. Combat air patrols apply to both overland and overwater operations, protecting aircraft, fixed and mobile sites on land, and ships at sea. Known by the acronym CAP, it typically entails fighters flying a tactical pattern around or screening a defended target, while looking for incoming attackers. Effective CAP patterns may include aircraft positioned at both high and low altitudes, so as to shorten response times when the attack is detected. Modern CAPs are either GCI or AWACS-controlled to provide maximum early warning for defensive reaction.
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