Photo of the 9/11 memorial taken from the World Financial Center, as it appeared in June 2012. Wikimedia Commons

9/11, by the numbers

Ahead of the 2017 observance of the anniversary of the Sept. 11 attacks, CNN compiled a list of statistics around the attacks and their aftermath.

19: Hijackers of four fuel-loaded U.S. commercial airplanes bound for West Coast destinations

2,977: People killed in New York City, Washington, D.C., and outside Shanksville, Pa.

2,753: People killed at the World Trade Center (WTC) site in Lower Manhattan

343: New York City firefighters who died in the initial attacks and subsequent collapse of the WTC towers

23: New York City police officers who died

37: Port Authority officers who died

2: Age of youngest victim

85: Age of oldest victim

184: People killed when hijacked American Airlines Flight 77 crashed into the Pentagon

40: Passengers and crew killed when United Flight 93 crashed near Shanksville, Pa.

1,641: WTC victims’ remains positively identified as of August 2017

$500,000: Estimated amount of money it cost to plan and execute the attacks

$123 billion: Estimated economic loss during the first two to four weeks after the WTC towers collapsed in New York City, as well as decline in airline travel over next few years

$60 billion: Estimated cost of the WTC site damage, including surrounding buildings, infrastructure and subway facilities

3.1 million: Hours of labor to clean up 1.8 million tons of debris

$750 million: Total cost of cleanup

22: Governmental agencies rolled into a single Department of Homeland Security, including the Customs Service, the Immigration and Naturalization Service, the Coast Guard and the Federal Emergency Management Agency, after 9/11