Category Archives: Travel

An automated collision avoidance system warned of a close call

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A reader writing as Pete808 left the following comment, which appears to provide additional details showing why our United flight to SFO on March 21 abandoned it’s initial landing attempt and powered up, went around, and made another landing attempt (this second one was successful).

Pete808’s findings show how much information can eventually be gleaned from existing public data.

Here are his findings, which initially appeared in a comment but are being elevated here because of their importance.

Here’s what I found by doing some additional internet research. By the way, I have no training or experience as a pilot or air traffic controller, although I’ve flown to SFO quite a few times.

In any event, one can go to LiveATC.net and listen to or download the archived air traffic control recordings for SFO for March 21, 2026. The archives are in half hour segments. After what seems to be a routine clearance to land, the archive for “SFO Tower” has a very cryptic communication from UA 373 a little more than halfway through the recording covering the time period beginning at 2200Z (Zulu or UTC time which is 3 pm SFO time). UA373 indicates that he’s going around although I couldn’t really tell what was being said by listening. In response, the tower controller tells UA373 to fly the runway heading and eventually to contact NorCal Approach.

If you review the archive for NorCal Approach for the period starting again at 2200Z, at around 23:45 into the recording the controller asks UA373 to say the reason for the go around and UA373 replies that they were responding to an RA. An RA is apparently a Resolution Advisory from the ACAS system (Airborne Collision Avoidance System), which is an onboard aviation safety system designed to prevent mid-air collisions by independently detecting nearby aircraft and advising pilots on avoidance maneuvers.

Although two planes landing on parallel runways is pretty routine at SFO with the aircraft required to maintain visual separation, the instructions with respect to ACAS Resolution Advisories is to do what the RA says. So even though UA373 was supposed to maintain visual separation from the other aircraft and even if that visual separation was still being maintained by UA373, when the RA was given by ACAS, the crew of UA373 was obliged to follow it.

Hope your health issues get resolved favorably.

More details surface on our apparent close call

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I am indebted to a reader who identified themselves simply as “Researcher” when leaving the following comment.

I had intended to post this earlier, but it was apparently lost in yesterday’s preparations.

I’m not an aviation expert, so please verify the data below before making conclusions.

ADS-B Exchange appears to show the other flight was a CRJ-200 operated by SkyWest as Flight 5974 from Fresno Yosemite International Airport. At about 3:16 pm PDT, United 373 and SkyWest 5974 were both approaching the airport at an altitude of about 1075 feet. It appears United 373 was gaining on the SkyWest, since it was traveling about 24 knots faster. SkyWest was to the front right of the United.

According to the Wikipedia entry for SFO, “aircraft may safely land side-by-side essentially simultaneously on 28L and 28R while maintaining visual separation.”

Here’s a screenshot of the track from ADS-B Exchange:

UAL373, SKW5974

You can view the data at this link, but use an adblocker. You’ll probably want to hit the pause button and reduce the playback speed to 1.2x or so:
https://globe.adsbexchange.com/?replay=2026-03-21-22:16&icao=ad1da9&lat=37.586&lon=-122.300&zoom=14.3

Flight audio?

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A reader who comments as “Bill” pointed to a possible source of audio from the flight.

Try this site for audio. https://www.liveatc.net/archive.php? KSFO Tower 10:00 UTC. I couldn’t get the archive file to load. But apparently the archives are suppose to be free for 7 days.

Maybe someone else can figure out how to access and then save an audio file. If so, it should shed even more light on the situation.

Still gathering data

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I reported our incident during landing in San Franisco Saturday afternoon to the NTSB over the weekend, and got an automated reply that it was being routed to the investigator assigned to the case. If there is one…

That’s another story, I guess. A haven’t been able to find any indication of a preliminary incident report being filed, although it seems that it might not have been posted online over the weekend. Someone else may have more luck. The search involves United Airlines Flight 373 from Honolulu to San Francisco during landing at SFO on Saturday about 3:15 pm Pacific Daylight time.

Data from the flight log appears on Flight Aware. It confirms that our flight was at about 1,050 feet altitude after passing over the San Mateo Bridge on its landing approach when it suddenly accelerated, quickly gained altitude, and then turned inland and circled around for another attempt. It was at that low point that Meda looked out the window and saw another aircraft below us. If we were just a thousand feet above the bay, as indicated in the flight log data, then only a few hundred feet separated us vertically from the other aircraft. It seems to me that this must required a report by report to filed by the pilot or crew.

I entered the location of our flight just as it broke off the first landing attempt and powered up and away, circling back toward the airport at about 5,000 feet altitude before making its second and successful landing approach. Then I entered the location in Google Earth, which produced this photo of our position about when the incident occurred. The red dot marks the United flight’s position.

Screenshot