Twenty-five years ago, 19 al-Qaeda terrorists hijacked four commercial passenger planes in a coordinated attack that killed 2,977 people in New York , at the Pentagon and in Pennsylvania.

The September 11, 2001 attacks unfolded in less than two hours , beginning when American Airlines Flight 11 struck the North Tower of the World Trade Centre at 8:46 a.m. United Airlines Flight 175 hit the South Tower just 17 minutes later, at 9:03 a.m.

A third aircraft, American Airlines Flight 77, crashed into the Pentagon in Arlington, Virginia, at 9:37 a.m. All 59 passengers and crew, along with the five hijackers, were killed, as were 125 people inside the Pentagon.

The fourth aircraft, United Airlines Flight 93, never reached its intended target. After learning through phone calls that other planes had been used in attacks, passengers and crew fought back against the hijackers. The aircraft crashed in a field near Shanksville, Pennsylvania, at 10:03 a.m., killing everyone aboard.

Who was aboard the four planes?

The four flights were travelling from the US East Coast to California , meaning they carried large amounts of fuel for their planned transcontinental journeys.

The 9/11 Memorial records 76 passengers and 11 crew members on Flight 11, excluding its five hijackers. Flight 175 carried 51 passengers and nine crew members, excluding five hijackers. Flight 77 had 53 passengers and six crew members, excluding five hijackers, while Flight 93 carried 33 passengers and seven crew members, excluding four hijackers.

The two World Trade Centre towers later collapsed. The South Tower fell at 9:59 a.m., 56 minutes after it was struck, while the North Tower collapsed at 10:28 a.m., 102 minutes after the first impact.

The attacks killed people from more than 90 countries and became the deadliest foreign attack on US soil. Twenty-five years later, ceremonies continue to honour the victims, with relatives gathering at the 9/11 Memorial in New York to read their names aloud.