Originally Posted by
BubbaLoop
According to the TSA, liquids pastes and gels are very dangerous, but bread renders them innocuous. Thus, peanut butter or jam in a jar is not allowed, but on a sandwich it is OK.
The same mysterious effect applies to pie crust. Pie crust can somehow take any amount of liquidy gel-like filling, and inert the threat it poses to aviation security.
http://blog.tsa.gov/2008/11/easy-as-pie.html