Here's one and there's more:
Introduction
Since 9-11 there has been much speculation about the possibility that the planes used on that day were flown by remote control. If you are not familiar with these theories it is advisable to read them first before reading this article.
These theories were sparked by a number of anomalies in the official story such as:
The alleged hijacker pilots have all been reported to be less than adequate pilots.
The jerking movements of the planes.
The aerobatic manoeuvres performed by Flight 77 prior to its crash into the Pentagon
The failure of all pilots on four planes to change the transponder code to 7500 indicating a hijacking is taking place. (They didn’t even need to change their transponder code; transmitting “squawk seven five zero zero” on the radio is enough.)
The bizarre way that AA Flight 77 flew round in a circle and into the side of the Pentagon like a plane coming in to land.
You can read these various pieces and come to your own conclusions. There has been a gradual evolution in this theory over the years since 9-11 as more evidence has come to light. Original theories focused on the idea that the planes were modified (probably in the airports) to allow remote control. Looking from the viewpoint of our unknown conspirators this might appear unnecessarily complex and risky, especially when compared to more recent ideas which we will expand on in this essay.
Tricking Air Traffic Control
The key concepts have been dealt with in more detail in Operation Pearl (A.K. Dewdney) and Rendezvous Points (F. Levi) but will be shown in summary here as follows.
Two planes flying on the same vertical line will appear as one spot on a radar screen.
The US military conceived of a plot in the ‘60s in which a remote controlled drone would be substituted for a passenger plane using this concept of “radar shadow”. The idea was to blow up the drone and blame it on a Cuban shoot-down as part of a fake terror campaign. See Operation Northwoods (Appendix B)
Three of the planes had the transponder disabled. The transponder transmits information about the plane's identity and altitude to Air Traffic Control. When disabled the plane becomes an unidentified blip on the radar, though ATC can manually tag the radar blip to keep track of it, as was the case with Flight 11 (ref)
United Airlines Flight 175 switched off its transponder for about 30 seconds then apparently changed its transponder code twice
If a switch took place it most likely occurred near an airport or airbase where the real plane would fly above the drone as just after it took off.
Why go to all this trouble? These conspirators presumably wanted to start the pre-planned war in Afghanistan. What would have happened if the suicide hijackers had changed their minds at the last minute, or crashed on the way?
(see flight maps)
http://www.the-movement.com/air%20operation/Flight11.htm