SAN FRANCISCO (AP) Asiana Airlines acknowledged in documents released Monday that its pilots failed to correct their fatally slow approach to a landing at San Francisco International Airport but also blamed the maker of the jet, saying it did not automatically maintain a safe speed.

Asiana wrote in the filing made public by U.S. accident investigators that the Boeing 777 had major design flaws that led the pilots to believe it would keep flying at the proper speed and failed to warn the cockpit crew in time when it did not.

Boeing Co. countered in its own filing with the National Transportation Safety Board that the airplane performed as expected, and the pilots were to blame for the July 6 crash because they stuck with a clearly troubled landing.

The Asiana flight slammed into a seawall at the end of a runway during its final approach. The impact ripped off the back of the plane, tossed out three flight attendants and their seats, and scattered pieces of the jet as it spun and skidded to a stop.

In all, 304 of the 307 people aboard survived. Coroner’s officials concluded that one of three teens who died, Ye Meng Yuan, was run over and killed by a rescue vehicle as she lay on the tarmac.

Asiana acknowledged in its NTSB filing that the crew failed to monitor air speed in the moments before the crash and should have aborted the landing for another go around.

“The probable cause of this accident was the flight crew’s failure to monitor and maintain a minimum safe airspeed during a final approach,” Asiana conceded.

However, Asiana argued that the pilots and co-pilot believed the automatic throttle would keep the plane going fast enough to reach the runway — when in fact the auto throttle was effectively disengaged after the pilot idled it to correct an unexplained climb earlier in the landing.

The airline said the plane should have been designed so the auto throttle would maintain the proper speed after the pilot put it in “hold mode.”

Instead, the auto throttle did not indicate that the plane had stopped maintaining the set air speed, and an alert sounded too late for the pilots to avoid the crash, Asiana said. The airline added that U.S. and European aviation officials have warned Boeing about the issue, but it has not been changed.

The NTSB previously said the pilots showed signs of confusion about the 777’s elaborate computer systems. The agency has not determined an exact cause of the crash.

Crew member Lee Kang Kuk was an experienced pilot with Asiana but was a trainee captain in the 777, with less than 45 hours in the jet. He has told transportation safety board investigators that he did not immediately move to perform an emergency “go around” because he felt only the instructor pilot had that authority.

Asiana wrote to the NTSB that under its company policy, “any pilot can and should call for a go-around — without penalty ‚— whenever confronted with a potential safety issue.”

Boeing told the NTSB the airplane and all its systems were functioning as expected.

“Boeing believes that the evidence supports the following conclusion: This accident occurred due to the flight crew’s failure to monitor and control airspeed, thrust level and glide path on short final approach,” the airplane manufacturer said.

Contact Justin Pritchard at https://twitter.com/lalanewsman.