A look back in pictures to the tragedy of 9/11/01:
Hijacked UA Flight 175 crashes into S.Tower of the WTC @ 9:03 am.
Spencer Platt/Getty Images
Flames spew out of the World Trade Center.
David Handschuh/NY Daily News/Getty Images
South Tower collapses. AP Photo/Richard Drew
The south tower collapses. AP Photo/Jim Collins
Smoke from the Twin Towers from the Jersey Turnpike. AP Photo/Gene Boyars
People run from the collapse of the towers. AP Photo/Suzanne Plunkett
Dust and debris fill the air. Jose Jimenez/Primera Hora/Getty Images
The World Trade Center on fire. Mario Tama/Getty Images
People fleeing the smoke and dust. AP Photo/Amy Sancetta
Rescue workers at ground zero. Keith BEDFORD/Gamma-Rapho/Getty Images
Firefighters make their way through the rubble. AP Photo/Shawn Baldwin
Firefighters work beneath the destroyed mullions, the vertical struts,
of the World Trade Center’s twin towers. AP Photo/Mark Lennihan
The rubble of the World Trade Center smolders. ALEX FUCHS/AFP/Getty Images
UA Flight 175 flies low toward the South Tower of the World Trade Center.
The Statue of Liberty, seen from a vantage point in Jersey City,
shrouded in smoke taken on 9/15/01. (AP Photo/Dan Loh)
A firefighter rests for a moment amid the rubble of the World Trade Center.
Matthew Mcdermott/Corbis Sygma
A man leaps to his death from a fire & smoke filled North Tower of the World
Trade Center. (Jose Jimenez/Primera Hora/Getty Images)
People covered in dust walk over debris near the World Trade Center.
(AP Photo/Gulnara Samoilova)
A construction worker discovered amidst the rubble of one of the collapsed
World Trade Center towers two intersecting steel beams that became known
as the World Trade Center cross.(PJ Media)
Sources: Flipboard, The Roosevelts, The Guardian, PJ Media