A faulty altimeter and apparent inattention by the pilots caused the Turkish Boeing 737 crash in Amsterdam, the accident investigation showed yesterday.

The investigators' preliminary report confirmed the widespread theory that the pilots let the automatic systems slow the plane to a dangerously low speed as it approached Schiphol airport.

At 450ft, as the pilots scrambled to speed up, it stopped flying and flopped on to the ground, killing the three flight deck crew and six others on board.

The radio altimeter had "told" the automatic flight system that the plane was 8ft below the surface when it was still nearly 2,000ft in the air. This caused the autothrottle to pull back the power to idle, as if the plane were touching down. Normally, pilots are expected to monitor the performance of the automated approach system.

According to a conversation recorded between the plane's captain, first officer and an extra first officer on the flight, the pilots had noticed the faulty altimeter earlier but did not consider it a problem and did not react, the chief accident investigator said.

With power almost non-existent, the automatic pilot attempted to keep the aircraft on its landing path and may have started "flaring", or pulling the nose up for landing.

The plane then slowed almost to stalling speed while still some way from the ground. The emergency warning systems came into action, sounding a warning and shaking the control columns to alert the pilots to the impending stall.

They applied maximum power but it was too late for the Boeing to regain flying speed and recover from the stall. The plane hit the ground at 110mph, the report said. While the main undercarriage sheared off, as designed, the nose wheel dug into the ploughed field, subjecting the flight deck to brutal deceleration. The pilots did not survive the violent stop.

The pilots' awareness of their predicament was dimmed because low cloud and mist prevented them from seeing the runway below and ahead of them as they began their descent from 2,000ft. However, the pilots would normally have been expected to react immediately to the autothrottle command to cut power, especially since they were aware that the radio altimeter was possibly faulty.

The radio altimeter is used in large aircraft as a supplement to the less accurate traditional barometric altimeters that take their reading from the pressure of the atmosphere.

The instrument panel in front of the pilots would have been displaying their correct altitude, taken from the main altimeters, while the usually more accurate radio altimeter was feeding into the flight system.

The description of the fatal final moments of the Turkish airliner contrasts with accounts from Turkey and some passengers of heroic pilots who saved a crippled aircraft from worse damage.

If confirmed, the failures by the pilots would make the Amsterdam incident at least the fourth in 13 months in which pilot error has caused an airliner to stall and crash. The others were at Madrid last August, near the French city of Perpignan in November and near Buffalo, New York, last month.

The initial accident findings are certain to intensify debate over the dangers of pilots losing their basic flying skills as a result of relying on the sophisticated electronics that control airliners through most of their flights.

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president