File photo of The World Trade Center south tower bursting into flames after being struck by hijacked United Airlines Flight 175 in New York City

The World Trade Center south tower (L) bursts into flames after being struck by hijacked United Airlines Flight 175 as the north tower burns following an earlier attack by a hijacked airliner in New York City in this September 11, 2001 file photo. REUTERS/Sean Adair/Files (UNITED STATES DISASTER POLITICS)