The crash of Asiana Airlines flight 214 last year occurred because the flight crew, relying too much on automated systems, incorrectly flew the plane during the landing, according to the National Transportation Safety Board.

Nearly a year after the Boeing 777 airliner arriving from South Korea crashed and caught fire at the San Francisco International Airport, ultimately killing three people and injuring nearly 200 others, the NTSB gathered Tuesday morning in Washington for a meeting that involved detailing why the plane went down on a clear day.

“Automation has unquestionably made aviation safer and more efficient,” Christopher A. Hart, the NTSB’s acting chairman, said during his prepared opening remarks. “But the more complex automation becomes, the more challenging it is to ensure that the pilots adequately understand it.”

The combination of reliance on these complex systems and a lack of understanding were key factors in the crash, he said.

“In this instance, the flight crew over-relied on automated systems that they did not fully understand,” Hart said. “As a result, they flew the aircraft too low and too slow and collided with the seawall at the end of the runway.”

In the aftermath of the crash, the NTSB began focusing its investigation on pilot error, saying that the plane was flying far too slowly to reach the runway when the crash occurred.

The pilot flying the plane was experienced, but lacked certain critical skills for guiding the aircraft, said Roger Cox, chairman of the NTSB’s operations group.

Three passengers were killed, and two of them were ejected from the plane. These two passengers were not wearing their seat belts during the landing, the NTSB said.

One of these two passengers was run over by two different firefighting vehicles more than 20 minutes after the crash, “something…that never should have” happened, Hart said. Multiple personnel thought she was dead, but they failed to check beyond visual assessments, investigators found.

On Tuesday morning, the NTSB released an animation showing how the accident occurred:

Last year, the NTSB released this footage of the accident last year:

This post will be updated.