I have not yet found any OTHER significant event which happened on this date. Perhaps other FReepers can help.
There are many "This Date in History" links, but one of the most comprehensive that I have found is at:
the Daily Miscellany
Also, the Oslo accords were signed at the WH on 9/13/93.
Original Camp David accords were 9/5-9/17 per another thread.
Lots of stuff here. The date was the first thing I thought of when I heard, but nothing connected until after I logged on here.
Of course, you have to think Middle East and/or bin Laden for anything like this.