New York City and the rest of the United States of America are marking 21 years since the 9/11 attacks on Sunday.

The National September 11 Memorial & Museum will host its annual commemoration ceremony to honor the 2,983 men, women, and children killed in the 2001 attacks at the World Trade Center site, the Pentagon, aboard Flight 93, and those killed in the February 26, 1993, World Trade Center bombing.

On sept 11 2001, 19 militants associated with Islamic extremist group al Qaeda, hijacked four airplanes, and carried out suicide attacks against targets in the United States. Two of the planes were flown into the twin towers of the World Trade Centre in New York, another hit the Pentagon and the fourth crashed in Pennsylvania.