You could be overthinking this. Case in point:

Bag arrives at IAH from CUN. Two things can happen:

1) Next flight is INTL --> bag goes to next flight
2) Next flight is Domestic --> bag goes to customs carousel

I seriously doubt the decision process accommodates any more complex and extraordinarily rare possibilities than this.

3) Next flight is Domestic connecting to Int'l --> bag goes to @:-)

Don't recall anyone posting about that.

Thanks again for the insightful information. Since ITI baggage seems to be only for UA-UA or UA-LH connection based on what I read here, that's why I was wondering if the scan read NH-NH, if it's smart enough to "translate" it to "UA-UA" and treat it as ITI. But based on what you said, do you mean as long as the next destination is an international destination, it will be treated as ITI regardless which airline code shown on baggage tag?

What percent of passengers going through IAH are making a I --> D --> I double connection? Is it even worth setting up a separate procedure for them?

Frankly, I suspect the percentage of passengers making the far more simple I --> I connection is already extremely small though obviously dwarfs this other obtuse double connection.

Family of four. US citizens. No GE but will have Mobile Passport App. UA flight all on same ticket. SYD -> IAH -> DTW. Arrives at 10:30 am. Departure 12:00 pm. Connection time of 90 minutes. Doable? Please and thank you.

Yes. Very.

The second flight is domestic -- the bag will come :eek:ut at the carousel in the customs arrival hall after the international arrival. No subsequent flights are going to be considered.

45 Min connection at IAH C to E gates
 

I have a 45 minute connection at IAH but looks like I will have to go from C7 to E15.
Can it be done?

Can it be done? Sure. UA wouldn't sell it otherwise. It meets the minimum connect time. But a lot of people would say it doesn't meet the minimal sensible time. What's your final destination? Are you okay with missing the flight for whatever reason? Just remember that the door is supposed to close 10 minutes before departure for domestic departures, so 45 minutes is really 35.

I think you can. Keep in mind either or both of those gate assignments could change three times between now and actual.

It's a 787-900 Sfo to Iah, I'm in the second row of Y.
Second flight is to Lga.
I'm traveling very lightly, anticipating having to run.
I've been following the flights for the past week. One time the first flight came into the E gates, but mostly C.
I'm in FC on a mileage upgrade for the LGA flight.
If I miss that one due to bad connection, and they don't upgrade me on the next (and last) flight to LGA, I'll ask for he miles back.
Would I qualify for downgrade compensation also? GG OVS DOWNGRADE?

It's doable but it is certainly a fairly long way from C7 to E15. And I have had some very long taxis at IAH that have turned 45 minute connections to 30 minute connections. Be ready to run/walk very fast, but most days you would make it.

You're assuming OP is connecting to a domestic flight. The MCT is 30 minutes for this flight whether it's international or domestic, but a passenger is subject to removal if not in the gate area 15 minutes prior to departure for a domestic flight or 30 minutes prior to departure for an international flight. So, 45 minutes is really 30 for a domestic departure or 15 (!) for an international departure. (Edit: OP specified destination)

C7 to E15 is nearly the worst case C to E transit. The United App gives a 21 minute travel time and suggests making use of SkyTrain. If OP were to run, it's likely possible to shave a couple of minutes off of that, and the train isn't a requirement; it's faster to take the train if it happens to be departing just as one arrives, but if there's much of a wait for the next train, it's likely faster to run.

If F is full on the next flight, your choices are to wait for a flight in F or take the next flight in Y. If your upgrade clears on SFO-IAH, you wouldn't technically be due any miles for IAH-LGA not clearing.

You would not qualify for downgrade compensation; the F cabin isn't oversold.

The risk tolerance question to OP is what the consequences are of a misconnect. There are eight nonstops a day IAH-LGA and an additional five to EWR. Thus, likely that if OP misconnects, he will find something.

But, if there is a mission critical event on the other end, this is not a connection I would book, given that there are five nonstops/day SFO-IAH, not to mention six nonstops SFO-EWR.

I book these sorts of connections, but I also understand that there is a risk. Be particularly attentive to the note above from jsloan regarding the T-15 gate deadline. While UA may not offload until T-10 or even later, if the flight is ready to go at T-15, it's unlikely to sit there. In addition, if the flight is overbooked and there is an oversale, UA will offload at T-15 to avoid paying IDB/VDB.