The Bojinka plot included plans to crash planes into buildings.
Various details here, with sources:
http://www.historycommons.org/entity.jsp?entity=operation_bojinka
-January 20, 1995: ‘First Hints of Bojinka Second Wave Revealed’
-May 11, 1995: ‘FBI Memo Fails to Mention Operation Bojinka Second Wave’
-June 3, 1995:'Plot to Crash Plane in CIA Headquarters First Mentioned in Media'
The June 3 entry includes the following:
"...in 2002 CNN correspondent David Ensor will comment about CNN coverage, “[E]veryone, all your viewers who wanted to, could have known that at one point Ramzi Yousef and some others were allegedly plotting to fly an airliner into the CIA headquarters in the United States, that, in fact, the idea of using an airliner as a weapon, that idea at least, had already been aired.…. We talked about it. We’ve done stories about it for years, frankly.” [CNN, 6/5/2002]
http://www.historycommons.org/entity.jsp?entity=operation_bojinka