Chek Lap Kok rescue teams sprang into action yesterday, plucking from the sea 120 survivors of a crash in which an airliner plunged off the north runway and broke in two. Tragically, 30 people died in the crash. Or, at least, they would have, had the 'crash' been real, and not a simulation designed to test the airport's emergency procedures. The Airport Authority said the annual exercise had fully tested the airport's response capabilities. The exercise, codenamed CLK 2004, swung into action just after 7.05am and ended just before 11.30am. Both runways were assumed 'closed' and 15 arrivals and 16 departures were 'cancelled'. Twenty-two fire department vehicles and 15 police emergency vehicles were involved. A Government Flying Services helicopter and nine ambulances took the 52 supposedly injured victims to hospitals around Hong Kong. The authority said the mandatory exercise tested the responsiveness of emergency services and allowed them to evaluate the adequacy of crisis procedures, emergency personnel, communications and equipment in case of an air crash.