On a recent Thursday I found myself with a few minutes available for plane spotting after work. I knew that United’s Star Alliance livery had landed earlier, so I pulled up Flightaware to check the departure time. The first thing I noticed was that there were a lot of planes in holding patterns. And there was a note in red indicating that inbound flights were being held at their origin cities for at least the next half hour.

I glanced up at the sky. It was a nice day, partly cloudy. No storms. Light wind. The weather shouldn’t be causing any delays. I looked over at the south runway. There were no signs of any issues – no paving crews or ARFF vehicles. I walked back to my car and pulled out my scanner. The frequencies were suspiciously quiet. I began to wonder… could the airport be ATC zero?

ATC zero means that there are no controllers on duty so the field is treated as uncontrolled. The most common reason for an airport to be ATC zero these days is covid. The tower and tracon are shut down so they can be thoroughly cleaned. This was not the first time it has happened at my airport. However, it was the first time it has happened during the busy travel season.

I saw some plane spotting friends by the north runway and they confirmed my suspicions. The airport was indeed ATC zero. One of the Centers (probably Indianapolis Center) was handling approach control, but anyone wanting to land or take off had to follow the same procedures used at uncontrolled fields, which involves calling out your position and intentions on a common frequency, and monitoring that frequency for other planes in the traffic pattern with you.

General aviation and business jet pilots tend to have more experience with uncontrolled fields. Perhaps unsurprisingly, the small planes that were coming and going during this time seemed to be pretty comfortable with the situation. Some of the commercial airliners, however, were clearly a bit less familiar with the procedures, as evidenced by one pilot who initially carried on with calling the tower, even though no one was in it.

I kept an eye on the Star Alliance plane while chatting with the other spotters. I was only half listening to the scanner, so we were all surprised to see a Southwest flight on short final suddenly turn to the south. It was quite unusual to see a commercial airliner make a turn so close to the airfield. In fact, I’ve never seen anything like it in the hundreds (thousands?) of hours I’ve spent watching planes at my airport. Then one of the other spotters saw the reason – a Cessna just crossing the runway threshhold.

The faster jet had gotten uncomfortably close to the smaller plane. I was pretty sure I heard the Cessna call out its position. Did the Southwest pilots miss the transmission? The Cessna landed and taxied off the runway while the Southwest flight did a 360 and got back onto the approach.

I got to wondering about the incident. The two planes seemed awfully close together. Did someone screw up? The next day I pulled up Live ATC to see if it could shed more light on what had happened. Turns out the Cessna did call out its position and the Southwest pilots heard it. The Southwest pilots continued to check in with the Cessna as both got closer to the field. Eventually the Southwest pilots realized they were catching up too fast and they announced their 360 turn.

So, just how close did the two planes get? When Southwest entered the pattern and called in, they were 15 miles out. The Cessna at that time claimed to be on “short final.” Southwest made calls at 11 miles out, 7 miles out and 5 miles out. At this point the Cessna called that they were still on short final. Southwest asked them to specify the number of miles and the Cessna said two, then amended that to a mile and a half. A few seconds after that Southwest announced their turn “at the inner marker.” Best guesstimate then is a three mile separation, possibly a little less. I believe this is within the regs… but it definitely looked closer than usual to me.

Ultimately, good communucation and situational awareness kept this from being an incident. Shortly after Southwest landed, the ATC tower re-opened and resumed control. It took a while for them to get everything sorted but I’m willing to bet no one complained. And the few minutes I had for spotting? Well it turned into a couple of hours. But I did finally catch that Star Alliance livery!