Original: The south tower (2 WTC) fell at approximately 9:59 a.m., after burning for 56 minutes in a fire caused by the impact of United Airlines Flight 175.
Simplified: United Airlines Flight 175, which crashed into the south tower of the World Trade Center at 9:02:59 a.m. local time (13:02:59 UTC). The south tower (2 WTC) burned for 56 minutes before it fell and was destroyed.