No.

I saw that ernestnywang replied No. Are you sure? IME in every other case I've come across, such segments have in fact counted: IAD-DCA, JFK-LGA, LHR-LGW...

Start to finish:-- no. Can start and end at different airports in the region
In the middle of a trip:-- yes

and I very nearly posted the same - but I re-read R2's post, and the question was about a surface segment between the starting point and the final destination; such surface segments do not count toward the 16 segment limit (and IMHO they should be called an open jaw not a surface segment)

As noted by others starting and ending an xonex at different airports in Japan is legal under the rules and does not require the use of one of your 16 segments.

Rule (e) states:

Does this mean that after several segments in North America, I can travel to South America and then have another stopover in NA before flying to Asia, for example?

At the moment, yes. For a while one of entries to NA had to be without stop-over. Before that, the situation was the same as at the present.

Which continents are possible to do with a DONE3 starting in Europe? I wanted to fly Europe-NA-SA-Europe, but then realized I can't backtrack from SA to Europe. So is it just Europe-NA-Asia?

Correct, just Europe/Middle East - North America - Asia

One of the rules is that you must visit each TrafficTariff Conference (TC) in turn with no backtracking
TC1 = North America and South America
TC2 = Europe/Middle East And Africa
TC3 = Asia and South West Pacific

ETA:
Should have thought of adding this earlier: - a snippet from the soon to be new wiki to this thread:

The ticket rules divide up the world into three “TrafficTariff Conferences” (TC) each having two continents; as follows:
TC1 = North and South America
TC2 = Europe/Middle East and Africa
TC3 = Asia and South West Pacific (SWP)
https://cimg2.ibsrv.net/gimg/www.fly...cbfe52fc9b.png
Notes:
Europe/Middle East includes the countries of North Africa (Morocco, Algeria, Tunisia, Libya, Egypt, Sudan)
Russia is split between Europe/Middle East and Asia (the split is at the Ural Mountains),

Main Routing Rules:

• You must visit all three TrafficTariff Conferences – you will of course be starting in one of them, so you must visit the other two in order (travelling either eastbound or westbound), and complete your RTW journey by returning to your starting TC; generally you must return to your starting country (there are exceptions - see More Rule Details below for more information)
• Within a TC, you can visit either or both continents
• Within a continent you can travel about in any direction you like

...

My husband & I have already started a DONE4. We bought our tickets through JAL & started our trip from Tokyo. One of our flight coming up is with Cathay SEA-HKG-BKK. In anticipation of those flights potentially being cancelled or Thailand issuing restrictions for passengers transiting through Hong Kong, I want to change our flight to JAL SEA-NRT-BKK. Cathay has already cancelled our original flight but rebooked us a day earlier on another flight. There is not telling if this new flight will also eventually be cancelled as the situation does not look good for Cathay at this time.

Providing seats are available & open for RTW passengers, would I be able to transit through my departure city (NRT)? I know I would not be able to do a stopover but this would only be a 2hrs layover. Our options are very limited as we have to cross the Pacific because we crossed the Atlantic at the beginning of our trip. The only possible routes from SEA considering this, are through HKG or NRT. Going through London with BA is not an option as it would add a continent to our trip unless a layover in a separate continent would be authorized without counting it as a continent. In the event that either Cathay cancels the flight with no possible rebook or that Thailand issues restrictions (like other countries have done), would JAL be responsible to get us to BKK through a different route & flight or would we be on our own to resolve this issue?

Just trying to get expert advices before calling JAL as often the agents do not know the rules. I'm trying to be as prepared as possible. Any help would be greatly appreciated.

I would call the American Airlines RTW desk - (800) 247-3247 - and explain your problem to the agents there. AA might be able to take over the ticket from JAL, or at least can help you decide on alternatives. There are various possibilities that would let you get to BKK without transiting Japan (your starting country) or via Hong Kong - e.g. SEA-DFW-ICN-KUL-BKK using AA and Malaysian. If those extra segments would put you over the 16 flight limit, AA has the ability to rewrite the ticket waiving that restriction. They've done so in the past during periods of irregular operations, e.g. strikes, airlines going under (such as Malev Hungarian or Air Berlin) and the coronavirus might be a similar situation. I'd call them regardless.

Thank you Gardyloo, great advice! I will try 1 more time with JAL on Monday as we would really prefer that more direct route of SEA-NRT-BKK. If that fails, I will definitely call AA RTW desk.

Any OW airline can make changes to a xONEx. You do not need to continue to deal with the airline that issued the ticket. Indeed dealing with airline of the flight you want to change can be the way to go (I have done that)

Until an official wavier is in place you have to go the xONEx rules. With a wavier can be more latitude with flights if your route becomes impossible. But airlines can play hard ball

As above on another route to your next stop (BKK?) via NRT/HND/ICN/SIN/KUL/where ever.
If you have run out of USA segments may need to pay for a separate flight to the (new) departure airport.
Have you used all the Asian segments?
https://en.wikipedia.org/wiki/Seattl...tional_Airport
https://en.wikipedia.org/wiki/Haneda_Airport
https://en.wikipedia.org/wiki/Narita...tional_Airport
https://en.wikipedia.org/wiki/Kansai...tional_Airport
https://en.wikipedia.org/wiki/Suvarnabhumi_Airport

Please let us know what happens. You will not be the only people trying to change flights in Asia

Edit
JAL fly LAX-KIX-BKK. and HNL-KIX-BKK. I suspect a little know routes.
Can AA get you to HNL? From PHX-HNL? Or pay for a flight?
https://en.wikipedia.org/wiki/Daniel...tional_Airport
https://en.wikipedia.org/wiki/Kansai...tional_Airport
Your full route would help getting more answers considering the 16 segment limitation

I haven't tried this recently, but it hasn't worked for the last couple of years. Maybe 6 years ago with a DONEx issued by AA I was able to simply change a LAN flight to the following day with a 2-minute call to LAN. A few years ago, however, LAN told me that now it had to be AA that made the change, and AA then said it had to "reissue" the ticket (all for a simple date change... not even a flight number change). This was especially annoying because the AA RTW desk kept US "banker's hours" and no other AA agent would touch the record. (AA has somewhat extended the hours of that desk, but still...)

Why simply rebooking a freely-changeable segment from a D class seat Wednesday to a D class seat Thursday on the same flight now requires a call to the originally ticketing carrier and a complete ticket reissue is not clear to me. It wasn't always that way.

Thank you Mwenenzi, those are all good advices! I don't mind re-positioning on our own dime to a different airport in the U.S. if necessary. I don't mind changing my date by a few days either.

To be honest, I'm not sure if we have used all our Asia or U.S. segments. Here are our segments NRT-DEL-DOH-SOA-land to EZE-SCL-LIM-MDE-MEX (this segment is via MIA as there were no direct flights)-SNA (this segment via DFW as no direct flights)-land to SEA-BKK (via HKG as no direct flights)-NRT. This is my first RTW ticket & although I did a lot of research last year before I booked the tickets, I'm pretty novice at this.

I definitely suspect many will want to change flights/routes in Asia. That's why I started this process last week in anticipation. I called JAL & at the time, they denied me saying although seats were available, they were not open to RTW passengers. They suggested I called them again in a week. Now that Cathay as officially cancelled many flights, it will get worse. Might get even worse if this continues. That's why I would rather change this in anticipation. JAL customer support in English is only open M-F. Cathay lines are totally jammed. Not sure if AA RTW desk is open on the weekend. I might give that a try.

I will definitely give updates as I move along in this process.