.....

That's a roundabout way of saying that like me you have no answer to the specific question the OP has asked ie how that calculation is made and where he can find the rules for that calculation

That's saying that it won't be, as proposed by the OP that it wont be a refund of ratio of distance travelled over total proposed travel

(quote from OP : For a partially-used ticket, I believe I’ve always received pro-rated tickets (refund in proportion to the distance of segments flown).

What it will be is a calculation for a business class ticket for the journey undertaken, which unless it is very close to start of journey likely to be close to zero

Himeno writes: "Even if the issuing carriers CoC says something, you're still bound by the fare rules."

Are you sure? If I buy an ordinary restricted nonrefundable AA coach domestic round-trip, the fare rules will surely sane nonrefundable. But if AA cancels a segment, there is no doubt in my mind that AA will offer a full refund to my oringal form of payment (among other options). And I believe they are required to do so precisely because their COC so provides (section "Involuntary Refunds"). In some respects surely COC does modify rights otherwise set out in fare rules. The documents interact in interesting ways -- sometimes directly contradictory, yes, but then it is a question of judgment to properly interpret the contradictions and determine the proper lawful result.

I think we've hit the crux of the question, Dave: Whether the method of calculation for a refund, subsequent to a carrier cancelling a confirmed ticketed segment for its own business reasons, is the "sum of the full fares" as provided in fare rules (for voluntary cancellations), or whether some other method of calculation of the refund is required in this circumstance. I still don't feel I know the answer -- and I am not convinced that the fare rules for voluntary cancellations truly dictate procedures in case of involuntary cancellations. But in any event it sounds like it's time to write to CX, see what they say, and then proceed from there.

In further researching this question, I found the following statements from the US Department of Transportation:

“refunds should be provided upon request to passengers who wish to cancel their trip as a result of a flight cancellation or significant schedule change made by the carrier” -- letter of 2001

"The second problem we wish to bring to your attention concerns passengers holding nonrefundable tickets or tickets that require the payment of a penalty for a change of flight time or travel date. It is our understanding that at least one carrier has been applying its nonrefundability/penalty provisions in situations in which the change of flight time or travel date has been necessitated by carrier action or "an act of god", e.g., where the carrier cancels a flight for weather or mechanical reasons. Imposing monetary penalties on passengers in these kinds of situations is grossly unfair and it violates 49 U.S.C. 41712, as would any contract of carriage or tariff provision mandating such a result. We will aggressively pursue any cases of this type that come to our attention." -- letter of 1996

I credit that neither of these statements specifically discusses calculation of the amount of a refund when a ticket has been partially used. Still, the language of the second quote could hardly be stronger -- "grossly unfair ... aggressively pursue". Calculating a fare difference using full-fares on flown segments, even when a passenger actually flew on a restricted fare with lower inventory and numerous other restrictions, would seem to fly in the face of these instructions from DOT.

I have contacted Cathay -- politely, of course, and with a brief request grounded in Cathay's COC rather than DOT rules. Will report back with any notable developments. Meanwhile, perhaps the above quotes can be useful to anyone facing a similar problem.

If the ticket was bought in Hong Kong for example USA DOT will not apply
USA law is only for the USA: not for the world
We have not got all the information IMHO: the full route as ticketed

OP - Are you trying to force a cancellation here??? rather than taking whatever rerouting is offered (given you assumedly have other segments)

If so I suspect any refund will be low (as per single fare pricing) and probably paid by CX only - I can't imagine CX has an easy way of splitting any refund across the remaining segments and carriers.


---

My only experience with CX on a semi-similar is on an ex-TPE J Class Business Saver TPE-HKG-xSYD-xHKG-TPE. Cost was about US$1500. Stopped over at Sydney and was unable to get leave for return flight within six months. Ticket cancelled and refund was US$200 which was explained to me as difference between my fare and a one way fare at time of ticketing. Admittedly it took 3days for them to work this out and they just refunded with no paperwork or anything (at the time I was ok with it as I frankly was expecting to get nothing back)

At the risk of repeating myself the OP is not cancelling the ticket he purchased . He has a confirmed reservation that the airline cannot honour, nor can it give him an alternate flight that is acceptable to him as required by the COC.
The only similar situation I have had was when I had flown the outbound segment of a return fare and the airline cancelled my return flight and wanted to put me on a flight 12 hrs later which was unacceptable to me. The fare rules stated that my ticket was not refundable but this does not give the carrier the right to keep your money if they cannot comply with their contract with you.
If I had cancelled the ticket for no reason i would have expected and received no refund. I requested a refund because of the airline's inability to provide the service. The refund I received was not the fare I had paid less the one way fare for the journey that I had completed (which would have resulted in no refund) but half the fare that I had paid ie it was prorated as the OP raised in his initial post.
While every man and his dog has provided an answer to the question what happens if I cancel my ticket for my own reasons, no-one is responding to the question that the OP is asking.
Clearly, my case where a simple return that cost less than the airline's lowest one-way tariff resulted in a 50% refund of the total ticket cost, the answer to the OP's is not as simple as what has been given here so far.

1. What does OP want for a result? It may be that he should be caerful what he wishes for. (Alternatively, what doesn't make sense to others, may make perfect sense to OP because we don't know what he wants & he doesn't say).

2. The one thing we know for certain is that OP can't fly his ticketed route. Why the carrier cancelled is of no consequence and it's immaterial. In the end, of course there's a profit motive, it's a for-profit business !

3. So what does OP want? Does OP want to be rerouted or does OP want a refund? As a technical matter, the COC of all carriers make this the carrier's option, but the fact is that I've never heard of a carrier which doesn't give the pax the first chance to see if there are acceptable alternatives.

4. If OP wants a refund, he need only decline whatever alternatives are offered, if any. His problem will be, as others note, that the calculation of refunds on intl. complex routings is murky and often leads to minimal or zero actual refund. As a starting point, rather than playing cat & mouse, get on the phone with the carrier and ask what the refund will be if OP cancels. OP can then fight about it if he doesn't like what he hears, but he might find it reasonable and not have to fight.

5. If OP wants a reroute, he should do the leg work upfront and propose the rereoute he wants. Bearing in mind the segment caps and the like, the key is to be reasonable. This is a reroute occasioned by a cancellation so any rule is waiveable. But, if what took 1 segment before now takes 5, that won't likely work.

6. All of this speaks to getting on the phone, not email and speaking with real live people to achieve the result OP wants. Right now sounds like games playing which always ends badly for the pax. The one thing carriers do well is enforce their own rules once things get bounced to their regulatory people which is where OP is headed.

So, like any good strategist, how to turn lemons into lemonade? Figure out what you want and devise a path to get there rather than simply stumbling from step to step just because you can.

Mwenenzi, do you have any authority (law, regulation, staff policy statement, etc.) for the proposition that US law and regulation does not apply to a ticket bought elsewhere for travel to/from/via the US? I believe you're mistaken. I see no such statement anywhere in applicable DOT rules. Indeed, I see statements precisely the opposite.

Often1 and Moa999, thanks the thoughts. I agree that it's time to contact CX, which is why I did so yesterday. Often1, you're right that I haven't said much in this thread about what I want for a result, but I feel that's my prerogative. Clearly my discussions with CX will be different, as I need to tell them exactly what outcome I seek (and I have done exactly that). Meanwhile, anyone similarly situated, in case of future cancellation or significant schedule change, can look to this thread for insights into passengers' rights in this situation. What I ultimately choose to do is of lesser interest to others, I would think. But clearly I'm thinking about refund rights, not just reroute rights, and I'm thinking about that because it's a potentially-desirable outcome under these circumstances -- albeit of course more desirable if the refund is substantial and less so if the refund is zero or tiny; hence the need to try to figure out how the refund would be, and should be, calculated.

It's a CX-issued ticket for a flight on AA. AA cancelled. I don't see CX refunding anything until it finds out how much AA will reimburse it.

That is simply that the US cannot apply such laws extra territorially; the DOT has no legal authority to make laws in Hong Kong

I disagree. By all indications, the DOT has authority to regulate behavior occurring in the US. And customer service matters pertaining to travel in or via the US are well within the authority the DOT has long enforced.

The DOT has numerous rules that explicitly regulate the conduct of foreign air carriers when they serve the US. See e.g. the Notice of enforcement policy: oversale notice for foreign carriers. By its plain language, this rule covers "foreign air carriers", and nothing in the rule suggests that this rule benefits only passengers originating in the US.

Analagously, many folks here may be familiar with EU rules on air travel disruptions. Those rules benefit even non-EU citizens when flights arrive, depart, or connect in the EU.

Nothing of this offends my sense of extra-territorial application of law.

Bedelman, by his own statements, admits that he is simply toying with FT. As others point out, he's going to have a rude awakening when speaking with CX and would be far better off armed with some good suggestions (something with which FT can be very good) from others who have experienced roughly the same situation.

As to DOT, it's by no means an extraterritorial application of law (which, by the way, isn't unlawful). If the ticket was purchased in the USA, originates or terminates, DOT authority is clear. Beyond that, non-USA carriers which are theoretically beyond DOT's reach, agree to regulation as a condition of a license to conduct any commercial operations here.

But, in the end, it's AA which cancelled the flight and all comes back to AA and how OP interacts.