This is an interesting excerpt from an AP article:
"The attack occurred exactly 2 1/2 years after the Sept. 11 terrorist attacks in
the United States _ and there 911 days in between the terror attacks in
Madrid and those in New York and Washington. It also was Europe's worst
terror attack since the 1988 bombing of a Pan Am jetliner over Lockerbie,
Scotland, killed 270 people".

My heart and prayers go out to the wonderful Spanish people.