Thank you.

That is rather interesting, and a surprisingly clear answer for JAL, which they are not known for giving on this topic. But all good if it works. Yes, JAL has luggage agreements with most airlines, and on a single ticket it will be checked through no issue, that is what these agreements cover. Separate tickets to non Oneworld airlines is usually not possible.

Personally I would still plan to not check a bag unless I had it in writing that JAL will check through to ET on separate tickets. As CPH-Flyer writes, this is not the norm, and I am rather risk averse. In other words, if you show up with a massive checked bag and the check-in agent and manager/supervisor doesn't allow you to check it through, what's your plan?

I have read much of the thread and have not seen a specific answer to my dilemma. We will be arriving on UA into NRT at 250p, and we are contemplating purchasing tickets on ZipAir at 5p to BKK. I understand ZipAir does not have an airside transit desk but I have read on their website that their system will automatically check you in and email you boarding cards. We will have carry-ons only. Do you think that we will be allowed to board airside without having to go to their outside counters?
Would you take a chance that ZipAir would permit us to transfer airside with their emailed boarding passes?
If not, we will be made to pass through immigration formalities to their counter in T1. I am also assuming that Japan will be open by our travel date of Jan 2023. Is there sufficient time to get to their counters by the 4pm checkin deadline if we arrive on UA at 250pm?

If you're going UA to ZipAir and you are certain you will your boarding passes sent electronically, then you're good to go. There will be no transit security coming in from the US, they will verify you have your boarding passes as you check in for UA and then as you leave the plane though. After that, you just walk from the UA gate to the ZipAir gate, which 2 hours should be enough unless your UA flight is seriously delayed. Both flights are in T1. Also worth noting, this only works because you're carryon-only.

The problem is on the return, you can't go from ZipAir to UA if that is your plan, as they will force you to go through security, which you can't do without an approved visa to enter, unless you are going from ZipAir to ZipAir on very specific routes:

Connecting flights | ZIPAIR Official Website

and

Regarding Transfers and Same-day Connection Services | ZIPAIR Official Website

I wouldn't plan around this until it is actually announced.

Really? It would be common for someone to not have their onward boarding passes when they board the UA flight. What if the onward carrier didn't have online check-in / electronic boarding passes? I think that all UA will do is confirm the onward itinerary, but not require a boarding pass.

Unless I'm misunderstanding the situation, I'm not sure I follow. Doesn't going through transit security put you in the same place that the UA deplaning flight would put you on the inbound direction? Why would you need admissibility to Japan to go through transit security?

My gut feeling is that it will be okay by then, but I agree - don't plan on or assume anything different than the status quo until such is officially announced.

What do people connecting on separate tickets do if they need to get a boarding pass? Thinking of arriving on UA and connecting to Thai on a separate ticket; what happens if I can't get a mobile boarding pass from Thai? Doubt they have a transfer desk.

They'll also allow a booking confirmation printout as well if you're going to get you're boarding pass at the gate at NRT, but since ZipAir will provide electronic boarding passes, that's all he'll need for proof of onward travel, which is all they require.

You don't need admissibility in to japan to go through transit security. Maybe I should have phrased it as "there's not even transit security" to make it more clear, but I didn't think that would trip anyone up. You're over thinking it. Point I'm making is there's nothing once you arrive, you are dumped into the terminal with no checks aside from them checking your onward travel as you are deplaning (based on my experience a couple months ago), which alleviates the time concern he asked about. ZipAir has non-standard requirements, and you can deduce that since there's not even transit security for incoming flights from the US, there would be no requirement to enter the country when switching to ZipAir, as you would if you were flying inbound on ZipAir on the return flight where you would be required to enter the country to transit unless you're on specific zipair to zipair routes.

UA and TG are both star alliance. It's very possible you can check through with UA to TG when you check in for UA at your origin, even with separate tickets. If not then you can probably get a boarding pass at the TG gate if you have time when you arrive, but hopefully someone can respond and provide confirmation.

I recently connected from JL to TG on separate tickets and had no problem checking in and getting a mobile boarding pass using the Thai app. If for some reason you are not able, you can get it at the gate which is in the same wing as UA no more than a 5 minute walk. Not to worry as once you are NRT, the #1 goal is to get you out of NRT.

I'm thinking of booking 2 separate BA award tickets (LHR-HND and HND-SYD) on JL using Avios, with a 12-hour transit in HND. Unfortunately the system won't let me book it as 1 ticket.

I'll be HBO. Can anyone see any problems with doing this?

No problems at all.

If its just an issue with booking it online, call BA?

On AA's website I had to do something similar for BKK-LAX due to a short layover I wanted to be on the same ticket, I couldn't book it straight through from LAX-BKK. Instead, I had to use multi-city booking and go BKK-NRT and NRT-LAX on the same day and it let me book them and put them on the same ticket. With a 12-hour layover though, there's absolutely zero problems with you having two separate tickets.

Connections at Narita seem surprisingly easy these days - no forms or checks of any type.

Now that I've seen it, I would consider connecting there more often, but the thing that worries me and will keep me away is the inability to enter Japan in case of an IRROPS situation, which seems like it would be a huge problem.

Also unfortunate that only one *G lounge is open, so it's kind of a madhouse.