A plane packed with more than 300 people slammed into the runway at San Francisco airport and caught fire, forcing many to escape down emergency inflatable slides as flames tore through the Boeing 777.
At least two people died in the crash last night crash, while another 181 people were taken to hospitals, most with minor injuries, authorities said. Five people, including a child, remained in a critical condition at San Francisco General Hospital, the region's main trauma centre.
The two people who died were found outside the heavily damaged jet.
As Asiana Airlines Flight 214 approached the runway from the waters of San Francisco Bay at around noon local time, travellers in the terminals and other eyewitnesses could see that the aircraft was swaying unusually from side to side and that at one point the tail seemed to hit the ground.
Kate Belding, who was jogging a few miles away, said she thought: "Oh my God. That plane is crashing."
By the time the flames were out, the top of the Boeing's fuselage had burned away. The tail section was gone, with pieces scattered across the beginning of the runway. One engine appeared to have broken away. Emergency responders could be seen walking inside the burned-out wreckage.
News of the crash spread quickly on Twitter and the internet, with eyewitnesses tweeting their stories, posting images of the plumes of smoke rising above the bay and uploading video of passengers fleeing the burning plane.
"It just looked really bad," Ms Belding said. "I've seen the pictures of it since then, and it's amazing anyone walked out of that plane."
The investigation has been turned over to the FBI but terrorism was ruled out, said San Francisco fire chief Joanne Hayes-White. Aviation and transportation investigators were heading to the scene and Asiana, Boeing and the engine manufacturer, Pratt & Whitney, pledged to work with them.
Vedpal Singh, who was sitting in the middle of the aircraft and survived the crash with his family, said there was no forewarning from the pilot or any crew members before the plane touched down hard and he heard a loud sound.
"We knew something was horrible wrong," said a visibly shaken Mr Singh, whose collarbone was broken. "It's miraculous we survived."
Mr Singh said the plane went silent before people tried to get out any way they could as luggage tumbled from the overhead bins The entire incident lasted about 10 seconds.
Based on witness accounts in the news and video of the wreckage, Mike Barr, a former military pilot and accident investigator who teaches aviation safety at the University of Southern California, said it appeared the plane approached the runway too low and something may have caught the runway lip - the seawall at the end of the runway.
San Francisco is one of several airports around the country that border bodies of water that have walls at the end of their runways to prevent planes that overrun a runway from ending up in the water.
Mr Barr said the landing gear or the tail of the plane may have hit the seawall. If so, it would effectively slam the plane into the runway.
Noting that some witnesses reported hearing the plane's engines rev up just before the crash, Mr Barr said that would be consistent with a pilot who realised at the last minute that the plane was too low and was increasing power to the engines to try to increase altitude. Mr Barr said he could think of no reason why a plane would come in to land that low.
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 were not immediately known.
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 US 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 January 17 2008 at Heathrow Airport in London. British Airways Flight 28 landed hard about 1,000 feet short of the runway and slid on to 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.
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% 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 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.