September 11, 2001
Please observe a moment of silence at 8:46 a.m. (1246 GMT) to mark the moment when the first plane hit one tower and at 9:03 a.m. (1303 GMT), when the second hijacked airliner crashed into the other tower, and again at 9:59 a.m. (1359 GMT) and 10:29 a.m. (1429 GMT) when each tower crumbled.