AMSTERDAM — A faulty flight instrument aboard a Turkish jetliner lowered the plane's airspeed, setting off warning signals in the cockpit and prompting the pilots to try and accelerate before it crashed in the Netherlands, officials said today. The Turkish Airlines plane carrying 135 passengers and crew crashed less than a mile from the runway at Amsterdam's Schiphol Airport shortly before it was due to land on Feb. 25. Nine people were killed. The pilots, who died in the crash, were landing on automatic pilot when the altimeter, a device that measures altitude, registered that the plane was flying lower than it actually was and instructed the plane to decelerate, officials said. The Boeing 737-800 had twice before experienced problems with its altimeter, said Dutch Safety Authority chief investigator Pieter van Vollenhoven at a news conference at The Hague. He said the Safety Authority has warned Boeing of the problem and asked the company to alert customers that when altimeters are not functioning properly "the automatic pilot and the gas system coupled to them may not be used for approach and landing." Boeing said it was reminding all operators of its 737s to carefully monitor primary flight instruments during critical phases, adding that it was carefully monitoring the fleet. The deputy chairman of Turkey's Pilot's Association, Ahmet Izgi, said during an interview with Turkey's NTV that the preliminary findings were "not satisfactory" and that it was odd the pilots didn't react to the altimeter.