The "Missing Planes" of Sept 11th

Been reading up on the latest conspiracy theories in the Fortean Times and other publications. Theres a lot of gossip alledging that 4 or 5 unspecified civilian aircraft disappeared during that morning, and “were shot down” (a hilarious but strangely possible claim,I know).

Specifically, it was claimed that the Pitsburgh airliner that crashed was downed by an AIM-7F Sparrow air-air missile, and not by desperate hijackers who were about to lose control to the aircraft.

Also mentioned, was the loss of an “airborne” Sikorsky helicopter at the Pentagon, though no proof ever materialised on that.

How on earth would anyone be anybody be able to shoot down an airliner (let alone 5 of them), and then keep it totally secret – make all the volumes of evidence, wreckage, reports, bodies, mourning families, costs and law suits dissapear ?

Another of the even more annoying ones was that a Global Hawk monitored the whole initial attack on the WTC – i think this is incorrect.