Asiana Airlines president reveals engine defect was 'probably not' behind San Francisco crash Aviation investigators are investigation whether crash was caused by mechanical failure, pilot error or landing short Controller saw aircraft clip the sea wall as it came into land Recordings show crew had no concerns before landing then tried to 'go around' 1.5 seconds before impact Analysts will examine air traffic control records, weather and aircraft maintenance issues and cockpit data recorders The airport's Glide Path system, which is designed to avoid runway misses in a variety of weather, was switched off Finding out the cause of the crash could take months or years, as there are numerous leads By Daily Mail Reporter and Reuters Reporter A plane spotter caught the moment Asiana Airlines Flight 214 crashed on the runway at San Francisco airport, where it spun around before coming to a stop in a cloud of dust and smoke. Fred Hayes had been filming planes taking off and landing about a mile away from the airport, when the Boeing 777 came in for its fatal landing. The footage, shown on CNN, comes the National Transportation Safety Board revealed that the crew of the aircraft, which was flying in from Seoul in South Korea, had misjudged their approach about seven seconds before the crash and tried to correct it. The footage, and a separate dramatic sequence of pictures, shows the entire crash, from the moment of impact, to when thick smoke started to pour out of the plane. Impact: Plane spotter Fred Hayes captures the moment Flight 214 cartwheels across the runway and crashes as it comes in to land at San Francisco airport Two Chinese schoolgirls died and more than 180 people were injured in the Saturday morning crash, which may have been caused by pilot error. A preliminary examination of the on flight recordings has revealed the communication between the cockpit and crew as the plane prepared to land. According to a NTSB spokesman, the landing appeared to be routine until the controller noticed the plane hit the sea wall. There were no prior calls for help before the impact. 'The speed was significantly below 174 knots, we're not talking about a few knots,' she said. A preliminary investigation of the aircraft's recordings showed the flight was cleared for visual approach, which was confirmed by the crew. Preparations were then made for the approach and the landing gear went down. The target speed was given as 137 knots, but no anomalies or concerns were raised. Seven seconds before the impact, a member of the crew called for speed to be increased, a stick shift was heard taking place before a call for a 'go-around' was heard 1.5 seconds before the impact. The call for a 'go-around' is used when a crew wants to abort a landing and try again. Readings from the plane showed that the throttles were idle and air speed was slowed below the target airspeed. A few seconds before the impact the throttles were advanced a few seconds and the engines appeared to respond normally. The pilots are now being tested for alcohol, drugs and fatigue as the NTSB asked members of the public who filmed or photographed the crash to share their information. The flight data was revealed after it emerged that the airport had switched off a navigation system that helps pilots make safe descents during bad weather. Experts said that pilots have grown to rely on the decades-old system, but that San Francisco International Airport has switched it off for the past two weeks while the airport updated the main runway. Flight path: A sequence of pictures shows Asiana Airlines Flight 214 engulfed in smoke after crashing in San Francisco The Instrument Landing System and Visual Approach Slope Indicator are dependent on the airport, rather than the aircraft, according to the Daily News. 'You're tired after a 12-hour flight, so it's nice having all these extra things telling you, "Hey, I'm exactly where I need to be,"' Kirk Koenig, a pilot, said. Without them, a pilot has to rely on an inflight computer, Mr Kirk, the president of Expert Aviation Consulting, said. Reports that the aircraft had landed short of the runway, were backed by two unnamed airport workers who said boulders at the start of the runway had been damaged. One source said the rocks had been split in half from the impact of the crash and the other said: 'Boulders from the sea wall [were] knocked 150 yards down the runway.' Black boxes from the aircraft, which record critical data of the flight, have been recovered from the wreckage and will help investigators understand what brought the craft crashing down. Investigators from the National Transportation Safety Board will also analyze the cockpit voice recorder and flight data recorder to uncover what happened. Wreckage: The ceiling of the plane was destroyed by fire, which forced passengers to leave from emergency exits on one side only What went wrong? Firecrews work to contain flames after a plane skidded onto a dirt area at San Francisco Airport on Saturday, killing two. Investigations are now underway to determine the cause Relief: Passengers comfort each other and sit on the edge of the runway after escaping the plane crash Debris: Part of the landing gear is left on the runway after Asiana Flight 214 crashed in San Francisco 'We think there was no engine defect,' airline president Young-doo Yoon said at a press conference in Seoul, South Korea, on Sunday. Four pilots - all South Koreans - were on board the plane and they rotated on a two-person shift during the flight, according to The Ministry of Land, Infrastructure and Transport in South Korea. The two pilots behind the controls at the time of crash were Lee Jeong-min and Lee Gang-guk. Yoon Young-doo said the pilots were 'skilled'. Three had logged more than 10,000 hours each of flight time, while the fourth had put in almost that much time, he added. Investigators are also looking into whether the jetliner landed short and clipped a sea wall which separates the runway from the San Francisco Bay before crashing. While the National Transportation Safety Board, which is investigating the incident, said it's too early to identify the cause, they are not ruling out 'pilot error' in the horrific crash. It emerged on Sunday that the plane's Glide Path system, which is meant to help planes land in bad weather, was switched off as it made its descent. The weather was dry and clear on Saturday. Aircraft safety experts said Glide Path was far from essential for routine landings, and it was not unusual for airports to take such landing systems off line for maintenance or other reasons. Black box: Greg Smith of the National Safety Board collects the flight data recorder and cockpit voice recorder from Flight 214 Inquiry: Asiana Airlines President and Chief Executive Officer Yoon Young-doo, center, leaves after a press conference. He said that it does not appear that engine failure was to blame Rescue: A woman is taken away from the airport's reflection room where passengers rested after their ordeal 'The pilots would have had to rely solely on visual cues to fly the proper glide path to the runway, and not have had available to them the electronic information that they typically have even in good weather at most major airports,' said Captain Chesley 'Sully' Sullenberger, the former US Airways pilot who gained fame with a successful crash landing on the Hudson River in 2009. 'What that means is that then the automatic warnings that would occur in the cockpit when you deviate below the desired electronic path wouldn't have been available either. So we don't know yet if that's a factor in this particular situation, but that's certainly something they'll be looking at.' Glide Path is a computerized system based at an airport that calculates a plane's path of descent and sends it to pilots in real time. San Francisco International has turned off the system for nearly the entire summer on the runway where the Asiana flight crashed, according to a notice from the airport on the Federal Aviation Administration's Web site. It showed the system out of service June 1-August 22 on runway 28 Left. Kevin Hiatt, chief executive of the Flight Safety Foundation and a former Delta pilot, said it was common for airports to take instrument landing systems offline for maintenance on clear days. Pilots use several other instruments and visual cues to land in clear conditions, Hiatt said. Escape: This photo was taken by Samsung executive David Eun who had been on board the plane Horror: The Asiana Airlines Boeing 777 crash landed just off the runway at San Francisco International Airport on Saturday morning, killing two passengers and injuring more than 180 Shock: People look across the water at the wreckage of the plane, which crash landed on Saturday morning Search: Transportation investigators examine the inside of the aircraft as an inquiry into the crash begins Report: The National Transportation Security Board begins work on its investigation into the crash 'All of those are more than adequate to fly an aircraft down for a successful landing on the runway,' he said. Sullenberger said the San Francisco runway safety area had been increased to avoid short landings. While the cause of the crash may not be known for months, The LA Times claims its sources say federal authorities are looking into whether the plane flew in too low and scraped the sea wall before landing and causing the tail to come apart. Aviation safety expert John Goglia wrote in Forbes that the aircraft could have landed in an unreinforced section of runway pavement and damaged its landing gear after landing short. He said the plane would have been difficult to control with damaged landing gear. 'Aerial photos of the crash scene at SFO provide important clues in the debris field - where parts of aircraft are strewn after impact,' he wrote. Here, a myriad parts of aircraft are seen immediately after the sea wall and well before the touchdown area for the aircraft. The chevrons seen in aerial photos of the runway are used to show pavement areas aligned with the runway that are unusable for landing, takeoff or taxiing. The following sequence of CNN graphics illustrate how the aircraft may have hit the lip of the sea wall, precipitating its fatal crash-landing. CNN Graphic: This image recreating the crash scene shows the aircraft begin its descent into San Francisco airport Recreation? Aviation analysts speculate the plane flew in low and hit the top of the sea wall which separates the runway and San Francisco Bay Out of control: It is believed the plane hit the lip of the sea wall causing it to skid along the runway Frightening: After clipping the sea wall, the plane's tail was shaved off and two schoolgirls were killed Coming to a standstill: The shaved off tail section rested several hundred feet from the main body of the aircraft, with debris from the plane littering the runway Debris in that area indicates a significant likelihood that the aircraft landed short. Debris began at the sea wall, which divides the airport runway from San Francisco Bay, and stretched for hundreds of feet away from the plane. While the crash occurred on a day with clear skies, USA Today reports flight crew were aware there was a problem. However, when the plane ditched down near the water, no fire trucks were there to meet the flight, raising questions about the state of radio equipment on board the Boeing 777. Investigators were due to arrive at San Francisco Airport at about midnight on Saturday to begin the inquiry into what caused the accident. Break: The snapped-off tail of Asiana Flight 214 landed off the tarmac, well away from the rest of the plane Under the leadership of Bill English, the team will work with the Federal Aviation Administration, the aircraft's manufacturer Boeing and Korea's Air and Accident Investigation Board. NTSB analysts in Washington, D.C., will examine air traffic control records, weather and aircraft maintenance issues, while investigators on site will examine the aircraft, cockpit data recorders, the scene and whether radios were down. Kevin Hiatt, CEO of the Flight Safety Foundation CEO Kevin said determining the cause of the crash could take months or even years. He told USA Today investigators are likely to provide daily briefings for a week with factual accounts of what is found and where they efforts are being focused. Chesley Sullenberger, a CBS News aviation and safety analyst, said the NTSB may also examine the runway construction following the fatal crash. The retired commercial pilot said the construction mandated by the Federal Aviation Administration is designed to move the runway further from the seawall near where the jet struck ground. Meanwhile, Kevin Darcy, a retired chief investigator for Boeing, said it is highly unusual for a plane's tail to come off. 'I just haven't seen anything like that for years and years and years,' he told USA Today. 'There's no way of knowing if this is the same circumstance, but the last time I saw a situation where the tail came off like that on landing was during the flight testing from a DC-9.' Emergency workers rushed to its aid and doused it with white foam to try to control the flames. Blaze: Flames tore through the plane which started spinning after its tail snapped off They were able to help those who were able to escape the wreckage and were seen fleeing down emergency slides. According to an excerpt of the radio recorded at the airport tower the plane was cleared to land at 18.21, just over a minute later the flight called in and appears to have called for emergency assistance. Fatal: A fire gutted the plane's cabin after the crash, which killed two people