"Then all of a sudden I saw what looked like a cloud of dirt puffing up and then there was a big bang and it kind of looked like the plane maybe bounced (as it neared the ground)," she said. "I couldn't really tell what happened, but you saw the wings going up and (in) a weird angle."
"Not like it was cartwheeling," she said, but rather as though the wings were almost swaying from side to side.
The flight originated in Shanghai, China, and stopped over in Seoul, South Korea, before coming to San Francisco, airport officials said. The airline said there were 16 crew members aboard, and the 291 passengers included 77 South Koreans, 141 Chinese, 61 Americans and one Japanese citizen. The nationalities of the remaining passengers weren't immediately known.
Airport spokesman Doug Yakel said 49 people were in serious condition and 132 had less significant injuries.
The airport closed for several hours, and when it reopened, two of the four runways were operating.
Asiana is a South Korean airline, second in size to national carrier Korean Air. It has recently tried to expand its presence in the United States, and joined the Star Alliance, which is anchored in the U.S. by United Airlines.
The 777-200 is a long-range plane from Boeing. The twin-engine aircraft is one of the world's most popular long-distance planes, often used for flights of 12 hours or more, from one continent to another. The airline's website says its 777s can carry between 246 to 300 passengers.
The flight was 10 hours and 23 minutes, according to FlightAware, a flight tracking service. The 777 is a smaller, wide-body jet that can travel long distances without refueling and is typically used for long flights over water.
The most notable accident involving a 777 occurred on Jan. 17, 2008 at Heathrow Airport in London. British Airways Flight 28 landed hard about 1,000 feet short of the runway and slid onto the start of the runway. The impact broke the 777-200's landing gear. There were 47 injuries, but no fatalities.
An investigation revealed ice pellets that had formed in the fuel were clogging the fuel-oil heat exchanger, blocking fuel from reaching the plane's engines. The Rolls-Royce Trent 800 series engines that were used on the plane were then redesigned.
Bill Waldock, an expert on aviation accident investigation, said he was reminded of the Heathrow accident as he watched video of Saturday's crash. "Of course, there is no indication directly that's what happened here," he said. "That's what the investigation is going to have to find out."
The Asiana 777 "was right at the landing phase and for whatever reason the landing went wrong," said Waldock, director of the Embry-Riddle Aeronautical University accident investigation laboratory in Prescott, Ariz.
"For whatever reason, they appeared to go low on approach and then the airplane pitched up suddenly to an extreme attitude, which could have been the pilots trying to keep it out of the ground," he said.
The last time a large U.S. airline lost a plane in a fatal crash was an American Airlines Airbus A300 taking off from John F. Kennedy International Airport in New York in 2001.
Asia remains one of the fastest-growing regions for aviation in the world. Even with slowing economies in Japan and China, airlines there saw 3.7 percent more passengers than a year ago, according to the International Air Transport Association.
Finding enough experienced pilots to meet a growing number of flights is becoming a problem. A 2012 report by aircraft manufacturer Boeing said the industry would need 460,000 new commercial airline pilots in the next two decades — with 185,000 of them needed in Asia alone.
"The Asia-Pacific region continues to present the largest projected growth in pilot demand," the report said.
Lowy reported from Washington, D.C. Associated Press writers Jason Dearen and Sudhin Thanawala in San Francisco, Scott Mayerowitz in New York and Pauline Arrillaga in Phoenix contributed to this report.