Richard, TM7 has a tinfoil hat in just your size. One of the last know words coming from the United aircraft was from a male passenger talking to his wife on a cell phone and he said: "I'll call you back, we're gonna try something." That is a fact! Not a "creditable witness", not a rumour, not a conspiracy, but a fact.
Again to apply a little, gasp, shudder, simple logic, do you not think that every radio frequency known to man was not being monitored? How do you think the news media often shows up at disaster sites before the police, firemen, medics or whomever? If not them, some old codger sitting up a holler somewhere playing with his shortwave radio? BUT NO ONE HAS COME FORWARD. NOT EVEN SOME KOOK WITH A TINFOIL HAT. Or perhaps, did the Wing Commander in DETROIT whisper to the fighter pilots before they left "we haven't the slightest idea of what is going on down there but you guys go down there, maintaining radio silence all the way,and blow that sucker, with 200 American civilians on board, right out of the sky." At no time did a fighter pilot call in and say "there appears to be some guy with a towel around his head driving. Don't know if the Captain hurt his head or it's a, gasp, shudder Muslim." To which the Wing Commander replied, "Makes no difference, it's worth 200 Christian Americans to take out 1 Muslim. Punch his ticket for his last ride."
Incidentally, going back to the Cuban hijacking days. The airlines have had a strict policy of total compliance with hijackers. If someone sticks their finger in their pocket and sez, "I've got a gun, knife, bomb, etc", the scene is played from a position of total creditability downward rather than the reverse. The subject of armed pilots has been broached several times and ALPA (Air Line Pilot Assoc--union) has been adamant that they are pilots not policemen. So the terrorist, or any hijacker for that matter, were only too aware that they were going against a group of people (pilots and cabin staff) charged with total compliance.
Now then, we have beat this dead horse so long in another thread that GB got on our butts. So's I'm outta here. (In my heart of hearts, I know the PA plane was shot down by Sylvester Stalone with a rag tied around his head, shooting a .45 calibre model 1911 (the special model that never has to be reloaded) from the window of a piper cub cruising @ 120mph as the United flight thundered by him @450mph. He precisely shot off one of the engines to fall in the lake and the resulting torque caused the aircraft to disentergrate as if hit by an air to air missile. Later, when asked about this shooting feat, he admitted that he was aiming at the hydraulic lines but got lucky.)