I can't believe I'm hearing this on a conservative forum, I expect a lot more informed opinion here...
important buildings are protected against car/truck bombs - underground garages have been closed in many cases, concrete barriers near entrances, streets closed, etc. a plane can fly into a building without restrictions.
nobody is talking about "banning small planes" - but there need to be more restrictions on allowable flight routes around major cities for sure.
Maybe we're here to learn something. Is this a problem?