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.