9-11: UA175; 42d Street, the Allentown PA story


The female lead in the stage play “42d Street” was a young woman from Allentown, PA. She was sometimes referred to as “Allentown.” I use the 42d Street reference to remind me of the story of three planes in the skies over Allentown on the morning of September 11, 2001.

The Three Planes

It has long been known that two of the hijacked planes on 9-11, United 93 and United 175, crossed paths on 9-11.The location has never been given much thought, but it was over Allentown. What is not known is that a third commercial aircraft of note also crossed paths with both planes in the same time frame over Allentown.

The three planes were well separated in altitude, but closely spaced, in time, United 93 westbound, United 175 southbound and a third plane eastbound.  United 93 was still climbing, United 175 was at altitude, and the third plane was midway between the two, altitude-wise. None of the three aircraft were a danger to the others and none were aware of their proximity.

The third plane was Midwest Express Flight Seven (MIDEX 7) the centerpiece of Lynn Spencer’s book Touching History.

Midwest Express Flight Seven

I will tell the MIDEX-7 story in an article currently in draft. For now, let me just sketch in the details.

According to the pilot’s account as told to Spencer, the path of MIDEX-7 was intertwined with and integral to the final moments of the descent of United 175 into the World Trade Center, South Tower. The story as told was sufficient compelling that Darlow Smithson Productions wanted to make it a vignette in its “Voices From the Air” production for National Geographic.

I was the consultant for Darlow Smithson and they tasked me to pull together the audio communications supporting the MIDEX-7 story. I found little of substance in the collection of air traffic control files provided to the 9/11 Commission and reported to Darlow Smithson that the vignette should not be used.

So, what happened?  As with many eyewitness and participant accounts of the day, the pilot’s recall compressed time and conflated events. He had internalized what he recalled, but what he recalled is not quite what happened, a story for another day.

The MIDEX 7 story is an interesting one, but it is not the story that Spencer told. MIDEX 7 was still over New Jersey when United 175 impacted.

MIDEX 7 actually crossed paths twice with UA 175, but it is the first crossing that concerns us here. So, back to Allentown we go.

United 175

At the moment American Airlines 11 impacted the World Trade Center, North Tower, the transponder code for United 175 changed to 3020.  That one change was all that was tactically necessary to introduce a Mode C intruder into the national airspace system. Such an intruder, a transponding plane without an associated data block, is not uncommon and controllers deal with the situation by asking the pilot to recycle the transponder. That is what the controller did that morning, except nothing happened.

By that time, the transponder code had changed to 3321, an unnecessary and extraneous tactical move by the hijacker pilot.  I am drafting an article to help us understand why the second code change was made.

Thus, by the time UA 175 was asked to recycle its transponder the code had twice changed but not to the original code as instructed.  The plane was a dangerous intruder into the National Air Space System and that fact was noted by an air traffic controller  when United 175 was over Allentown, PA.

“A Sky Filled With Chaos, Uncertainty and True Heroism”

On Monday, September 17, 2001, Charles Lane, Don Phillips and David Snyder, Washington Post Staff Writers published an article with the title, above. It was about specific hijacked planes but the skies over Allentown suddenly became the focus.

The authors report that while the controllers were looking for American 11, “a controller glanced at another radar screen and shouted, “Look. There’s an intruder over Allentown.”

That was a reference to United 175 under its new code of 3321, a lethal intruder which made a broad U-turn over New Jersey and then plummeted at 6000 feet per minute in the direction of 42d Street. Intruder code 3321 impacted the World Trade Center, South Tower at 9:03 EST.