OP - Make a claim to UA for 400% of the value of the segment, capped at $1,350 (the current maximum). Keep the complaint to 3-4 short declarative sentences. All that matters is that you were checked in prior to T-30, and at the gate by T-15 (UA's published minimums), that you had been off-loaded and the flight closed. That's all that matters. The rest is all fluff. What the cop, the TSA guy said, whether the GA was rude --- none of it matters. UA can see when you checked in and when you were off-loaded.

If you are compensated, all to the good. If you are not, pursue the DOT complaint and see what happens.

Sorry, that is not correct.

The DOT IDB rules apply to all commercial aircraft with 30 or more seats.

Aircraft with capacity of 60 or fewer seats may be excepted but only based on weight/balance issues:
14 C.F.R. 250.6.

That exception obviously does not apply here. OP was told he was offloaded because he was too late. And the flight went out full.

There in fact likely was a DOT violation.

Moreover, there is no requirement that a complaint be based on a "DOT violation." Even when the issue falls outside existing DOT reg, a complaint may be appropriate because:

1. It helps DOT identify problem areas for future regulation.
2. It adds to the published complaint statistics.
3. It will be forwarded to UA for response, and will receive higher level attention than if made through the normal customer care channels.

Yeah, but you can't offload a passenger who bought a seat until 10 minutes prior to departure, domestically. The gate screwed up, they should own up to that.

Read what I wrote again. You just said the same thing. I said the GA screwed up. It is all on the GA. The plane was full so technically it could close door and go. 2 separate things.

My buddy was a chief dispatcher at a certain airline that's no longer around a long time ago, and a GA tried to pull this shenanigan on him by pushing the plane back earlier and with an empty seat on board. My buddy walked over to the payphone, called his buddies in dispatch, and dispatch actually ordered the aircraft to go back to the gate to let him on. The GA was fuming, but she knew better than to try to retaliate, since my buddy reported to the airline's CEO from time to time regarding operations work...

I think another time a CO GA pulled a similar stunt on pax without realizing the pax was Larry Kellner, CEO at the time. She quickly found herself unemployed.

+1 I got to the point I never filed a complaint via the feedback, as it was seldom responded to. I would only file a complaint with the DOT, and it would for sure be responded to.

I've had this very thing happen to me on UA 3 times in the past 4 years.

If a passenger's boarding pass was scanned by the TSA, e.g. mobile or Pre-Check, the airlines are able to see if the passenger cleared security, but to my knowledge, not when.

Thanks, I did not know that. Learned something new today :) ^

Wait, you say Pre or mobile. Also plain old regular BPs I assume?

The boarding pass has to be scanned. In regular screening lanes, I don't think the TSA scans paper passes.

Huh? I've definitely had my paper boarding pass scanned to get through security.

Of course they do.

Did you mean the advice and conclusions that you posted after those two sentences? ;)

Whether it's a IDB or not (and others have already cited the rules for it), the DoT has a service complaint form on their website that can be used for any service related complaints. If this wasn't a service related issue, I don't know what would count as one.

The only reason why I wouldn't start whit a DoT complaint is if the OP wants to try and salvage the EQMs. For that I would start with UA.

You can tell it's been a while since I went through a regular line with a paper boarding pass.

I believe that is 15 minutes per the CoC for domestic flights except Guam and PR; 30 minutes for international flights, Guam and PR. I don't know where you got 10 minutes.

People confuse the cut-off with the door closing. They can offload pax at 15 and they close the door (theoretically) at 10.