This map here marks Johnstown area (location of Shanksville) and Camp David (on Catoctin Mt.) in yellow:
And here's the UA93 flight route, as per 9/11 Commission:
When the plane went down, the path was indeed pointed right at CD. (Angle's off if DC"s the target, albeit only about 15 degrees).
I think you have hit on something here!
I remember clearly FOX reported early on, before the location of the real crash in Shanksville was announced, that there had been a crash at Camp David. For a brief period after Lancaster Cty. was specified as the location of the real crash, there was confusion with reports of possibly two crashes in PA.
The next day there was brief speculation that CD had been the target, dropped soon after.
I laughed it off at the time - why bother hitting an empty vacation residence? This seemed to be a canard to win sympathy for Dubya. My idea was that the only target for 93 that made sense (given how the rest of the operation went) was the Capitol: spectacular visuals, highest building for many miles around, guts the legislature, maybe even kills a few Congress critters (dispensible politician martyrs). Make Congress meet in some industrial convention center, then they'll know who's boss. (I figured anthrax was then Plan B as the message to lawmakers.)
But now that you mention it ... the fact that there was talk of a crash at Camp David BEFORE the location of the actual event was revealed as Shanksville - pow! If they don't know yet where the real crash is, how then do they randomly assign it to Camp David? It suggests a prior script being executed, prematurely, before news gets around that reality had not conformed.
And Stickdog's thinking on this makes eminent sense. Camp David peace talks were held Sep 5-17, 1978, so it was in a sense the anniversary period. Hitting CD would have made a very coherent script for the purported Qaeda operation, wrapping the authorship up neatly.