You need to write this up with United please asap. Aside from the rudeness and incorrect information from the gate agent along with the assault for which he really should be terminated, there are two posts now referencing rogue agents at SFO telling customers it’s mandatory and that needs to be stopped immediately.

Not sure if it's the same system as they are using in the US or a different one, but I had a strange experience at TLV a month or so back.

Walked up to the machine, it took my photo, and then claimed I had already boarded. Gate agent seemed confused and asked me to try again - with the same message. Eventually after much tapping on her keyboard, and asking if I had already passed through the boarding area before (obviously not), she waved me through.

Other than the possibility that it actually thought someone that boarded before me was me (unlikely, especially given that I was in the 1K pre-boarding groups, so there weren't a lot of people before me), the only thing I can think of is that it somehow triggered twice for me - but there didn't seem to be any indication of that.

I wrote customer cares, who confirmed that biometric boarding is optional for US citizens. They were gracious and said they would be in touch with the station- we shall see I guess.

Discovered one disadvantage of this process last week.

Had a middle seat in Premium Plus, so went to the gate and asked them if they could try and get me an non-middle when they processed the upgrades to Polaris. They said sure, printed a 2nd copy of my boarding pass so I could keep my current paper one, and I went off to wait for boarding.

They hadn't called my by the time we got to boarding, so I presumed they hadn't been able to get me another seat, so I went to board. Photo taken, passport checked, and just as I was about to walk through I commented not to worry about a new seat - at which point the gate agent realized who I was and handed me the new boarding pass she had printed for me, with a new seat assignment. If not for me mentioning it, I would have sat in the wrong (older) seat, with the annoying confusion that causes when someone else comes along to sit in the same seat...

With normal boarding-pass-scanning boarding the machine would have beeped to advise them that my BP had the wrong seat on it, but obviously there's no process for that to happen when using biometrics. (And yes, I know a mobile boarding pass would have worked better, but I like paper!)

Facial Recognition
 

Does UA use facial recognition. I was boarding at LAX recently. I got to the boarding pass scanner and GA said hello xxxxxx. I scanned blmy boarding pads and it beeped that i already checked in. I looked to the GA who said, I already checked you in because I saw you waiting in the gate area. I'm a 1k and was on a F ticket.

Yes they do -- even at EWR they are using it more and more -- on our last flight to Japan on UA it was in use for our flight...

.....and it's still not faster than scanning the BP.

I can’t wait to travel with the twins when this hits

Wait a sec, did the gate agent said that he/she "checked you in" on the flight just cause the agent saw you waiting on the gate area? There are so many red flags with that if that is the case. What if you decided not to take the flight? They wouldnt know cause they scanned you onboard manually and now the system thinks that you are onboard! and there is no way an agent can remember mentally if the person that he/she marked on board actually went on board.

I think this is different than the facial recognition machine that all the replies so far is assuming / referring to.

United do NOT use facial recognition in any way related to what you've described. In fact, the whole flow you've described just makes no sense, and would be a breach of multiple policies (both United and probably even federal)...

In early January and late February 2024 at GUM, facial recognition was used immediately prior to walking down the jet bridge. This was instead of scanning our boarding pass (and did take slightly longer, having to stand still for a few seconds).

The facial scanning was done for international departure (MNL), but not domestic (SPN).

UA’s (useless) facial recognition technology does not work like that; you have to go up to the scanner and stand there while it takes your picture.

The gate agent likely used some other mechanism to identify you (gender, ethnicity, 1K bag tags, overheard someone say your name, etc.). It’s still awkward and weird, but it’s not Big Brother crowd facial recognition awkward and weird.

Yes, these facial recognition boarding are used in conjunction with international flights and are linked with CBP for exit records. Delta has them too and it has been used for at least 5-6 years now. But what OP describe is definitely way out of line if the agent truly did that.

The only way that it could work as OP suggested would be if the airlines could call up pictures from CBP without having that person actually stand at the scanner, which seems to be the sort of thing that somebody would have reported by now.

Hopefully there is an opt-out because I am less than remotely interested in sharing my biometrics with a corporation