The pilots aboard the Asiana Airlines Boeing 777 that crashed in San Francisco relied on automatic equipment - an auto-throttle system - to maintain airspeed and did not realize the plane was flying too slowly until it was just 60 meters above the ground, the head of the US National Transportation Safety Board said on Tuesday.

In her third detailed briefing on Saturday's crash that killed two Chinese passengers and injured more than 180 other people, NTSB Chairwoman Deborah Hersman also said two flight attendants were ejected from the plane after its tail hit a sea wall in front of the runway and was torn off. Both were found injured but alive on the side of the runway.

Hersman said many questions remained about the incident. The South Korean airline's flight crew were not tested for drugs or alcohol after the crash, a requirement for pilots of US-based carriers involved in accidents, she said.

The accounts given to investigators by the pilots, as relayed by Hersman, confirmed information from the plane's flight data recorder that showed the plane was traveling 25 percent below its target airspeed as it came in for landing.

The Civil Aviation Administration of China said on Wednesday that it has sent two specialists to the United States to track an investigation into the fatal crash.

The experts, who will be participating in the investigation as observers, arrived in San Francisco early on Wednesday, the CAAC said.

According to an annex from the Convention on International Civil Aviation, any country whose citizens suffer serious injuries or death in an aviation accident can send observers to track the investigative process.

The world's largest pilots union rebuked the federal board's handling of the investigation, and said it had released too much information too quickly, which could lead to wrong conclusions and compromise safety.

Releasing data from the flight's black boxes without full investigative information for context "has fueled rampant speculation" about the cause of the crash, the Air Line Pilots Association International said in a statement on Tuesday.

ALPA said the board had not provided enough context, and urged it to "elaborate on factual material that has been excluded from public releases but must be considered in determining not only what happened, but why".

NTSB spokeswoman Kelly Nantel said the agency routinely provided factual updates during investigations.

In a separate development, Chinese Foreign Ministry spokeswoman Hua Chunying said on Wednesday that the Chinese consulate-general in San Francisco is providing counseling for those affected by the crash.

Reuters-Xinhua

(China Daily 07/11/2013 page12)