Surviving a plane crash
Aviation safety experts say passengers were able to survive the Asiana Airlines crash on Saturday because of how planes have been strengthened in response to previous crashes.
While wheels are designed to break away beneath a plane, the fuselage and seating have been strengthened to protect passengers, experts say.
"It's because of what we've learned from past accidents and that's due to great accident investigation techniques and taking what we've learned about what's failed about the structure of the airplane," said Kevin Hiatt, CEO of the Flight Safety Foundation.
"They hit very hard, they skidded down the runway and then into the dirt and then really rotated around. It's great design characteristics that kept everything intact on that airplane so that people could actually evacuate."
Boeing's 777 is generally considered a safe plane since being introduced into service about 20 years ago.
The National Transportation Safety Board, which investigates crashes, has recorded 57 incidents involving various models of the Boeing 777 since May 14, 1997. The latest incidents include:
The most serious accident occurred January 17, 2008, when a Boeing 777-200ER, British Airways flight 38, crashed just short of the runway at London's Heathrow airport.
That crash had no fatalities, but dozens were injured. But in contrast to Saturday's warm weather in San Francisco, that winter crash was blamed on ice crystals clogging the fuel line on a long flight from Beijing.
"We can generally say it's one of the safest airlines in the sky," Hiatt said. "Other than that, this aircraft has got a great safety record. It's one of the safest airliners up there."
The Federal Aviation Administration investigated two accidents involving Asiana within weeks of each other in November 1998.
Even when commercial planes crash, passengers are often able to walk away. In a study of incidents from 1983 to 2000, the NTSB found that 95.7% of all occupants survived. Out of 568 accidents, 2,280 of the 53,487 occupants died.
Researchers at Massachusetts Institute of Technology have said the fatality rate of 0.2 for every 1 million airline departures makes air travel safer than other forms of transportation, including escalators.
"The statistics are such that commercial aviation is incredibly safe," said John Hansman, an aerospace professor at MIT and director of the International Center for Air Transportation. "One of the ways that we do this is making the airplanes as crash-worthy as possible when you do have an incident like this, where there was apparently a problem on landing."
A major factor in surviving the San Francisco crash was in getting the passengers off the plane before it burned.
Hansman said airlines must certify they can get passengers off a plane within 90 seconds in an emergency. A key to that is persuading passengers to leave behind laptops and other belongings and simply leave quickly, he said.
"If people had dawdled getting off this airplane, that would have put them at increased risk," Hansman said.