To avoid more incidents like the one in Austin that resulted in a plane being crashed into an IRS office, I would suggest that no plane be cleared for takeoff without a flight plan first being filed and that it be verified.
Even if a private pilot wants to just cruise around the skies a bit, some general info should be on file: i.e., will be flying north of the city or whatever, and if the plane deviates from the flight plan, the pilot be warned over his/her radio of this deviation and that fighters will be scrambled and the pilot forced down unless the situation is clarified.
This cuts into freedom of the skies, but since 9/11 and 2/18 (of this year), the skies aren't as free as they once were. If we ever get out of a wartime status, these restrictions should be lifted; in fact, there should be a "sunset" provision in the law or regulation that is put into place here.
Any suggestions are welcome here.