After the initial blade fracture, Captain Kevin Hunt had disengaged the plane's autopilot. When Hunt asked First Officer David McClelland which engine was malfunctioning, McClelland replied: "It's the left.... It's the right one". In previous versions of the 737, the left air conditioning pack, fed with compressor bleed air from the left (number 1) engine, supplied air to the FLIGHT deck, while the right air conditioning pack, fed from the right (number 2) engine supplied air to the cabin. On the 737-400 this division of air is blurred; the left pack feeds the FLIGHT deck but also feeds the aft cabin zone, while the right feeds the forward cabin. The pilots had been used to the older version of the aircraft and did not realise that this aircraft (which had only been flown by British Midland for 520 hours over a two-month period) was different. The captain later claimed that his perception of smoke as coming forward from the cabin led them to assume the fault was in the right engine. The pilots throttled back the working right engine instead of the malfunctioning left engine. They had no way of visually checking the engines from the cockpit, and the cabin crew — who did not hear the commander refer to the right hand engine in his cabin address — did not inform them that smoke and flames had been seen from the left engine.