While headed to lunch yesterday I spotted a small aircraft flying low overhead. I didn't think too much of it until a few minutes later the exact same plane flew over again in the exact same spot! I pulled up a flight tracker on my phone and saw that it was flying in the following strange pattern:

a screenshot of the flight path on ADS-B Exchange
Link to the flight path on ADS-B Exchange

The flight path consists of two back-and-forth passes in an East-West arc, six loops of a North-South oval, and two larger and more rectangular loops that end over Andrews Air Force Base. I'm struck by how precise the flying seems. What's more, looking up the flight path later it looks like the plane flew the same pattern in a different location later that same day, just rotated in a different orientation:

the second flight path, with the arc now North-South and the loops East-West

What is the purpose of this strange flight path?


1 Answer 1


After doing some research I believe this aircraft was inspecting or calibrating the ILS (Instrument Landing System) at the two airfields it flew over: Andrews AFB (ADW) and Danbury Municipal Airport (DXR).

Compare the flight path shown in this answer to the question "What is flight inspection, as provided by Cobham Aviation Services?", which shows a similar path consisting of an arc and loops, described as "to inspect the performance of the Instrument Landing System." Similarly, this YouTube video "FAA Beech 300 King Air performing CALIBRATION FLIGHT at Boston International" shows a nearly identical flight path.

Actually, the aircraft shown in that video, a Beech 300 King Air, is the exact same type of aircraft I saw:

screenshot of ADS-B exchange aircraft details

I assumed it was a bug or missing data, but apparently the registration is actually only 2 digits, as also seen in the video. Even the "flight number" matches the video, and gives us a clue as to the flight's purpose: FLC for "flight check."

  • $\begingroup$ You have correctly answered your own question! This was a Flight Check aircraft making sure that the radio signal from the ILS behaved as expected. Not sure this question should stay open, however... may be a duplicate. $\endgroup$
    – randomhead
    Commented Jan 31 at 17:37

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