I’m looking into this but the short answer is that since UA 175 was always transponding there was never a search only (primary) track. The “no primary” reference is to the original code, there was no continuity in the system as there was with AA 11.

Here is what happened. Al Shehhi changed the UA 175 code to 3020 shortly after AA 11 impacted the north tower. That caused the former track to go into coast on the air traffic control scopes and then fade since there was no longer a related data block. A new transponding aircraft showed up as what air traffic control calls a Mode 3 or Mode C intruder with code 3020, but with no data block attached.

Such an intruder is uncommon but happens often enough that controllers know what to do as Bottiglia did–have the pilot recycle his transponder. Such intruders happen when pilots forget to change codes when transitioning from one sector to another after being told to do so by the losing sector.

In sum, UA 175 never “disappeared” it was always there, first under its original code, then as code 3020 for four radar sweeps and then as code 3321, thereafter. Bottiglia and others never noticed the 3020 intruder, they were too busy with everything else, but he/they did notice the 3321 intruder.

Interesting find on your part and interesting to know that some folks are curious about UA175. I am toying with the notion of writing an article on “UA175, the forgotten plane.”

Miles

Ergo, he had confirmation, but not from Atta directly.

I’ll wait for Brian to catch up on my other email address.

Miles

The logic is a bit tenuous, but here goes. First, most all cross-country orientation flights were made on United. Second, United allowed and allows passengers to listen in to the cockpit. Atta and al Shehhi would have known that. Third, AA 11 and UA 175 were on the same frequency for a period of time; I’m not sure that Atta and al Shehhi could count on that, but it is my estimate that they used the knowledge about listening to the cockpit. Completely without proof I intuitively believe that Atta’s transmission, “we have some planes,” was meant for al Shehhi to hear. So, given that al Shehhi knew that Atta had control of AA 11 he then took over UA 175 soon after it entered ZNY airspace and before Atta impacted the north tower. Then, al Shehhi would have seen the black smoke, if not the fireball. I sat in the cockpit of a UA 767 with the Senior Pilot and confirmed that al Shehhi could have seen the NYC skyline; plus he knew what he was looking for. It is also, without proof, that Atta waited to give the order to purchase tickets until he had some degree of awareness that the day chosen would be good weather-wise.

Whatever the tactical plan, there is no question that al Shehhi changed the transponder code immediately after AA 11 struck. Now, that also happens to be about the time of the odd transcript entry you mention. So, two things. One, it is a reference to AA 11 or, more likely, it is a reference that they lost the secondary on UA 175 original transponder code and didn’t see a primary because there was none, the aircraft was now a Mode 3 intruder. It was never primary only to the FAA radar system.

And to close the loop back to the beginning of the day. Atta and al Shehhi knew both teams had cleared security at Boston. There was a confirming phone call.

Tobias, thanks for the sleuthing and what do you think about the notion of detailed planning between Atta and al Shehhi? Were you aware of the ability to listen to the cockpit on Channel 9 on UA flights?

Miles

There may be something further in my notes or Raidt’s notes if HC uploaded them. Lisa Sullivan won’t have notes and she likely prepared the MFR by listening to the audio recording of the interview. At some point NARA will release the audio files, but that won’t happen any time soon. I’ll keep looking, you’ve tweaked my interest. Thanks for the lead. I’ve copied the relevant para from McCurdy, below, simply to document them in this thread. Miles

[U] McCurdy recollected that at the time of the crash into tower 2, the display on
Ballenger’s monitor still showed VAL 175 at 31,000 ft, having just deviated from the
normal flight plan and heading into a big tum back east. The track on Ballenger’s ASD
was frozen long after it was known the plane had crashed into tower 2.
[U] Rubie Green interjected that the program was designed to maintain a tag on a flight
as it moved across the map from center to center. Various code changes would not affect
the track as it appeared to the dispatcher. McCurdy said that the ASD provides a rough
track of a plane’s progress; minute alterations in the flight plan wouldn’t be reflected on
the dispatchers display because such details only mattered to the pilot and the air traffic
controller. “The purpose of the track is to keep the plane out of the path of a
thunderstorm,” McCurdy said.

I did accompanied Team 7 to visit United Airlines (and American) but I don’t recall the specific discussions. I will look through the History Commons stuff and the NARA MFRs to see what I can find. Without proof, and given what McCurdy recalled, it is possible that someone did enter a flight plan update for UA 175 into the system, other than the one from 15 minutes earlier. And I don’t recall the details of that update either.

If you run across anything else please let me know. I will put this on my plate of things to do. I’m trying to stay focused on the larger task of applying Chaos Theory but it is interesting to track down more discrete events, Delta 1989 being one example, and now UA 175.

Thanks for the interest and for the input.

Miles