09:03 South tower crash
United Airlines flight 175 crashed into the south tower 17 minutes later. The plane caused an explosion on impact and sent a plume of fire out of the opposite side of the building.
Many people in the south tower witnessed the first crash and were already trying to leave the building. Some office workers had been told to remain at their desks, resulting in possibly fatal delays. Some people above the fires chose to jump to their death rather than wait for the flames.
Hundreds of firefighters and police arrived at the scene to help the office workers escape.