The Bureau of Civil Aviation Security has sounded an alert to all airports including the one in Tiruchi in the wake of a terror attack at Istanbul airport in Turkey on Wednesday. So, the visitors’ gallery has been closed for a week from Wednesday. A special security meeting was organised. It was presided over by the Airport Director K. Gunasekaran. CISF officers and other agencies participated in it. The sources said CISF personnel guarding the airport round-the-clock have enhanced patrolling and surveillance in key areas as a precautionary measure.