National Transportation Safety Board (NTSB) investigators conduct first site assessment of the wreckage of Asiana Airlines Flight 214, at San Francisco International Airport in San Francisco, California in this July 6, 2013 handout photo. U.S. officials examined flight information recorders and began investigating the crash of the Asiana Airlines Boeing 777 that burst into flames upon landing in San Francisco, killing two teenaged Chinese students and injuring more than 180 people, officials said on Sunday.