On the contrary; anyone who is aware of the complement of weapons possessed by the United States (and indeed, most of the industrialized nations of the world) can say with certainty that there is no such weapon in existence at this time. People like, say, military members (such as myself, and leftysergeant, and BStrong in this very thread), who actually WORK WITH weapons, sometimes on a daily basis. THERE IS NO WEAPON THAT CAN BE MODIFIED TO FIRE FROM A PASSENGER JET THAT WOULD BE ARMED IN THE TIME ALLOTTED. Is that clear enough for you?
Missiles do not fit the criteria you have outlined. Other projectile weapons do not fit the criteria you have outlined. THERE IS NO WEAPON IN EXISTENCE CURRENTLY THAT FITS THE INSANE CRITERIA YOU HAVE OUTLINED. The weapon would literally have to arm itself in less than one-quarter of a second, and even if you were able to disable the normal arming procedures to allow it to arm itself quicker (which, as others have pointed out, is impossible), it still could not arm itself that fast.
Here's a challenge for you, tmd; I highly suggest you go on
www.fas.org and look up the information they have on all projectile weapons. They gather the information on weapons from all over the world, so you'll find information on everything from handguns to missiles (the unclassified information anyway). You might actually learn something about weaponry, namely that it is impossible, given current technology (much less 2001 technology) to do what you are suggesting. Look up ballistics weapons and kinetic-energy weapons, which are the two types projectile weapons are typically divided into. Once you've done that, take a look again at what you're suggesting happened, and maybe you'll realize that IT IS IMPOSSIBLE. Plain and simple.
A) Do yourself and me a favor and work on your reading comprehension, because that is not what I said.
B) Physical evidence was discovered of the plane. Oh it wasn't all in one piece, but they found pieces here and there, such as the landing gear lodged in the aluminum cladding, the engine that landed on the street, the window frames within the wreckage, and while they weren't at all salvageable or usable, parts of the black boxes WERE found, IIRC. There were also bits and pieces of the items you mention above found within the debris; parts of telephones and computers; again, not whole, but parts existed that told us what was contained within the buildings. Same goes for the bodies; the bone fragments you mention, while not part of a whole body, tell us that people DIED there within those buildings. You do not need the entire sum of its parts to know that two planes struck those buildings, or that the buildings were equipped with typical office furniture, or that PEOPLE, actual living PEOPLE were killed there. By the logic you are advancing, the fact that the buildings were no longer standing, despite the gigantic pile of rubble, means they were never there, and we both know how ludicrous a notion THAT is. So again I reiterate; there was absolutely NO physical evidence discovered of a projectile weapon. No pieces of a missile (and trust me, they would have found them); no evidence of detonation, no leftover bits of whatever incendiary would have been used to propel the weapon (rocket fuel being quite different, chemically speaking, from jet fuel, and they found evidence of jet fuel as I recall).
Teams of people, both civilian and government, spent MONTHS combing through the debris, both on site and at the Fresh Kill landfill where much of the debris was sent; these are people who were trained in what to look for, and who would have recognized evidence of some kind of weapon other than the giant plane (which, given the manner it was used, qualifies as a projectile weapon itself anyway) that plowed into the buildings at 500+ mph. They found NOTHING. So again I tell you that your notion of a weapon fired from the plane literally an instant before the plane itself hit the building is ludicrous, laughable, and just makes you look like a completely insane person who has no grip on reality. Educate yourself as I suggested above, and maybe you might come to understand why nearly everyone in this thread is reacting the same way as me. Until then, I'm through with you.