Manual Skills

Part of San Francisco airport's automated landing system was out of operation at the time of the crash. The control tower told the pilots to fly a "visual approach," meaning they had to rely on other systems, visual cues and manual skills.

The NTSB's two-day agenda is filled with pilot-training and air-safety experts from Boeing, Asiana and the Federal Aviation Administration, and pilots from Boeing and Asiana, including the first pilot to ever fly the 777.

It also includes an academic researcher who has studied pilot interactions with automated cockpit controls for decades. Nadine Sarter, a professor at the University of Michigan, is also a member of an FAA working group that recently recommended 18 areas where safety could be improved, such as pilot skill and cockpit equipment design.

Autopilot systems are highly accurate and reliable, and some airlines require pilots to use them until just before landing, so they can minimize the chance of mistakes.

But the increased complexity "sometimes results in pilot confusion and errors," the working group said in the report.

Some pilots say they are increasingly programming flight controls rather than flying the plane itself, which diminishes their feel for the aircraft, and their ability to respond when something unexpected happens.

After the July 6 crash in San Francisco, the NTSB said the pilots appeared not to notice that the plane was well below its target landing speed and was dangerously close to stalling.

The Asiana crash has been compared with the 2009 Colgan Air flight, in which the pilots did not respond properly to a stall warning as the plane slowed dangerously just before landing near Buffalo, New York. The crash killed 50 people, including one on the ground.

Days after the Asiana crash, the FAA issued new rules on flight training that stemmed from the Colgan Air accident, that increased the flying time required for co-pilots to 1,500 hours, the same as captains, up from 250 hours.

The Asiana crash has also raised questions about how pilots are paired on flights.

Lee Kang-kook, the pilot at the controls of the Asiana flight, was attempting his first landing of a Boeing 777 jet in San Francisco and his supervisor, Lee Jeong-min, was making his first flight as a trainer. It was also the first time the two pilots had flown together, the NTSB has said.

A third pilot, part of a relief crew, was in a jump seat behind them. The fourth pilot, also part of the relief crew, was in the cabin.

According to the NTSB investigation, the pilots did not react when the plane slowed below the target landing speed of 137 knots (158 miles per hour) as it approached the runway, speed essential to keeping the jet aloft.

With less than a minute left in the flight, and the plane less than 1,000 feet off the ground, the speed slipped below 137 knots. Moments later, at just 103 knots, the pilots tried to abort the landing. But the plane was too close to the ground and struck the sea wall.