Identifying Check the cause Causation of the disaster Catastrophe proved Coming_to_believe difficult , as the accident Catastrophe had occurred Presence before the age of cockpit voice recorders .

The Department of Civil Aviation took Action action to ensure that operation of the automatic pilot on-off control on Douglas DC-3 aircraft was made distinctive from operation of any other control in the cockpit , and that instructions Education_teaching were issued impressing on pilots that gyroscopes should be un-caged prior to takeoff .

Approximately thirty minutes into the flight , the hijackers forcibly breached Attack the cockpit and overpowered the pilot and first officer , allowing Preventing_or_letting lead hijacker and trained pilot Marwan al-Shehhi to take over Change_of_leadership the controls Control .

They made Action several unsuccessful attempts to contact the cockpit .

These include increased battery life on underwater locator beacons , lengthening Expansion of recording Recording times on flight data recorders and cockpit voice recorders , and new standards for aircraft position reporting Reporting over open Openness ocean .

The hijackers stormed Attack the aircraft 's cockpit 46 minutes after takeoff .

Shortly after reaching Arriving cruise altitude and while the captain was out of the cockpit , he locked Hold the cockpit door and initiated Process_start a controlled descent that continued until the aircraft impacted Influence a mountainside .

Shortly after reaching Arriving cruise altitude and while the captain was out of the cockpit , he locked Hold the cockpit door and initiated Process_start a controlled descent that continued until the aircraft impacted Influence a mountainside .

In response Response to the incident and the circumstances of the co-pilot 's involvement , aviation authorities in some countries implemented Action new regulations that require Imposing_obligation the presence of two authorized Preventing_or_letting personnel in the cockpit at all times .

Three days after the incident , the European Aviation Safety Agency issued Statement a temporary recommendation for airlines to ensure Action that at least two crew members—including at least one pilot—were in the cockpit for the entire duration of the flight .

The investigation Criminal_investigation showed Statement that the crew did not issue Communication an emergency call Request despite the plane 's recurring warnings Warning and highlighted Expressing_publicly the lack of discipline and organized Arranging environment in the cockpit .

Less than 35 minutes into the flight , the hijackers stormed Self_motion the cockpit and forced Causation the passengers , crew , and pilots to the rear of the aircraft .

The spreading fire also burned Damaging through crucial electrical cables that disabled Destroying most of the instrumentation in the cockpit , forcing Causation the plane to divert Motion to Cincinnati/Northern Kentucky International Airport .

Investigators determined Deciding the cause Causation of the accident Catastrophe to be failure of the autopilot system and poor cockpit crew performance .

The third , Flight 1 , crashed Motion near Miles City , Montana after a design and manufacturing Manufacturing error allowed Preventing_or_letting an intense fire to develop Coming_to_be in the cockpit .

An investigation found Know several shortcomings in the airline 's operating Military_operation procedures , in particular lack of proper cockpit communication and mutual control Control of the descent and approach Arriving plans .

This was in part caused Causation by the airline electing Choosing to not follow Self_motion the Sterile Cockpit Rule and that a passenger was sitting Motion in a cockpit jump seat during the flight .

although not the pilot in command , according to the cockpit voice recorder transcript , the first officer james polehinke ( the only survivor of the crash Catastrophe ) was the pilot flying Being_in_operation at the time of the accident Catastrophe .

Recommendations from the inquiry Scrutiny led to Causation the mandatory installation of cockpit voice recorders in British-registered airliners .

Investigators with the United States Department of Commerce 's Civil Aeronautics Authority ( CAA ) , a predecessor organization to both the FAA and the NTSB , determined Deciding that an intense fire had developed Coming_to_be in the cockpit shortly after the aircraft had departed Departing the airport .

although the state of the wreckage prevented Preventing_or_letting investigators from definitively pinpointing Aiming the exact origin of the fire , an area of severe burning was found Know close to the unk fuel valve located in the cockpit between the pilot and co-pilot .

The CAA recommended Convincing that the cross-feed fuel system be relocated Removing to allow Preventing_or_letting for easier maintenance and inspection and to reduce Cause_change_of_position_on_a_scale the possibility of a cockpit fire caused Causation by fuel leakage .