[snowwrestler]

This is not true; the difficulty in using raw radar returns to manage and defend the domestic airspace was the primary reason the FAA grounded all civilian aircraft on 9/11--to clean up the scopes.

Andrews scrambled two (unarmed) F-16s to intercept flight 93; they just followed the Potomac north because no one knew where that plane was. Even after the PA crash was confirmed, those fighters spent hours contacting radar returns to check them out and get them to land.

[mikeash]

That just shows that primary radar is difficult to use, and that it's hard to track a plane on radar after it's crashed. I'm not disputing that. Perhaps "no real problem" was bad phrasing, what I meant was that they were able to track them and they were not "unable to locate" the planes.

[snowwrestler]

Ok, thanks