A number of people have argued that there was a gap in the radar trail of AA77 and that a plane swap may have occurred. It is true that Indianapolis Air Route Traffic Control Center (ZID) lost the trail when the transponder was interfered with, causing a period in which there was some confusion about the location of the plane. That confusion is, however, not relevant to the present discussion which is necessarily based on recorded data. Primary radar (skin reflection) tracking of the aircraft was recorded all the way to the Pentagon, as will be shown below.
John Farmer and Tom Lusch put a lot of work into examining the radar data. There were seven radar stations which picked up the plane on the course of its flight, three of which continued to record its position after the transponder signal was lost: QDB, QWO and QBE. One of the seven, QHY, located at Higby, WV, was only 56 nautical miles (NM) from the plane and would have received a strong signal, as radar is reliable to 200 NM. QBE was 167 NM so would also have been reliable. The plane was in range of QBE for the whole of the period in question.
For clarity, signals from just four stations are shown in the image below (Fig. 1): IAD, PLA, QBE, and QHY. The transponder signal was lost when the plane was travelling south at about latitude 38.64 degrees, as illustrated by the sudden cessation of signal from QHY. It is clear that there is no break in the radar signal, thus there was no opportunity for an undetected plane swap. If a swap occurred we would see the QBE track diverge and another take its place, but no such tracks can be seen. It has never been disputed that the plane was correctly identified as it left Dulles, hence one can safely conclude that the plane which hit the Pentagon was AA77.
Fig 1. Radar coverage is continuous from Dulles to the vicinity of the Sheraton Hotel
The persistence of the “radar hole” myth is one of the numerous puzzling features of the 9/11 narrative. The 9/11 Commission report is clearly deceptive regarding this issue. Perhaps they preferred to allow the public to go on thinking that there was an intentional lack of coverage in the area rather than admitting that the software which is supposed to analyze the radar input in real time was defective. Only if the data is correctly assembled and presented immediately to ATC officers will it be useful for the purposes of maintaining control and safety. There have been complaints for many years that the radar handling software is defective, allowing aircraft to become “invisible” to controllers if the transponder fails. and It is reasonable to suspect that this false information was deliberately allowed to stand by the Commission as it provided one more item among many to cause argument among 9/11 activists. It is a sad state of affairs that the untiring work of Tom Lusch, in his attempts to improve ATC performance, has largely been ignored.