The rules literally state "... of the price of the ticket ..." which is wide open to interpretation, but not necessarily the sector cost of the actual ticket. There have been a few reports that it may be 75% of the cost of the IATA point to point fares, or even 75% of the cost of the entire ticket. In any case info about successful claims of large magnitude is scarce - possibly this may relate to confidentiality clauses in such settlements.

You are not entitled to any flight coupons, free tickets etc. Actually, you are not entitled really to much anyway. You might get more, but don't expect much. A duty free or taxi voucher maybe.

I would also think it's fair to say that if you're on a carrier with a D RTW ticket that would downgrade you to coach even if there was an empty seat in A that you or another passenger could have been upgraded into, your chances of compensation are exactly zero.

If you find yourself in such a situation (well, really anytime you get downgraded, regardless of whether there was an upgrade opportunity), and you have the time flexibility and there's another ow carrier that can get you to your destination, I would think that pointing this out would greatly increase your chances of being accommodated. The carrier has to know that you can change the ticket to another carrier rather easily (and with zero cost and without even an endorsement let alone reissue if the other carrier operates on the same route), I would think that if you made it clear to them that that's what you'll do if not accommodated as ticketed, then magically some other passenger would be found that could be downgraded ahead of you.

Not necessarily. In the first 2 of my involuntary downgrades this trip, the flight is 1-class (was 2-class when ticketed) and while there is another airline operating the route it is with another alliance. On a full fare ticket a transfer to the other airline is feasible, but on xONEx which are discounted tickets it depends on the goodwill of the ticketed airline.

In my case, Comair did consider putting me on South African (but only after I asked if this was an option). But schedules and my tight timing precluded me taking the option up. I did get a voucher as compensation for 1 flight, but it is a token amount. For the 2nd flight check in was by contract agents who were not authorised to deal with compensation so I am waiting to be contacted by Comair.

I still have several more invol downgrades on this DONE4 ticket and will report how those go as I come to them.

Only a very few routes have more than 1 Oneworld carrier, but you often can change the date. The majority of city pairs served by Oneworld have precisely 1 carrier that can be used on OWE ticket. JNB-LHR certainly falls into this category. Also OP was probably flying the first sector, which has special rules (any changes require refund of the ticket and buying a new one, so not really an option in this case, and BA knows it).

My own guess is that the maximum compensation you can get these days is 75% of the sector purchase price (the OWE addon sector cost); and even that will rarely be offered. The airlines could claim that this represents the cost of the single sector (not unreasonable, as it is close to the 1/16th price of the ticket) and courts would accept that. Though discovery to determine how the OWE fare is allocated would be fun.

I flew JNB-SYD on an AONE5 several days ago and was invol downgraded to J when QF substituted a 4 class a/c for a 2 class a/c.

Both QF in JNB and in SYD said that because the aircraft was substituted and as a result we were involuntary downgraded that we would be entitled to a refund for the fare difference between F and J. From their calculation, they said we were entitled to US$1,100. They said that had the invol downgrade occurred on the day of travel rather than two days before, they would have refunded the money to us at SYD. However since they said the invol occurred two days before the flight that we would have to speak with AA about it (AA in CPT issued the ticket). We were given invol downgrade certificates upon check-in in JNB.

QF also said that even with the rules of the AONE5 that we were entitled to the refund since this was an involuntary situation.

Can anyone help clarify the situation?

Importantly, Qantas flights not originating in Europe are not subject to EU regulation 261/2004 so facets of compensation like "75% ... of the price of the ticket ..." do not automatically come into play.

I guess that stated entitlement could be considered a reasonable hassle-free compensation offer given the situation.

I am now under the impression due to BA being a European carrier I am entitled to 75% of the sector or ticket difference, the reason for this is the EU legislation.

IB fly JNB-MAD-LHR.

I was replying to AA EXP DFW-LON's post and have made that clear.In this case, you are entitled to 75% "... of the price of the ticket ...".

Here's the full text of the relevant part regulation (No 261/2004):

There is an interesting thread on the BAEC forum where a claimant states he and his partner each received from BA 75% of the entire fare paid for J RDU-LON-AMS-LON-RDU for being downgraded AMS-LON. It incident happened in September '07 and BA eventually credited the amount in November '08.