I'm a non lawyer, Nizar.
I'd have thought the 'duty of care' here is the safe transfer to your destination at the given time on the given date.
It's a bit of a stretch IMHO to say the provider (QF in this case) has to be specific about the precise mode of delivery.
A swap from A380 to a cruise would be materially different from a switch to a 747 which AFAIK remains an acceptable mode of pan-Pacific transport.
Speaking as a non lawyer !
PS: I was swapped once - not happy but I didn't think much of it. Stuff happens !!!
Lol I didn't mean to sue them etc, so not talking about 'duty of care' as such, but more on the lines as to whether they would go to any reasonable lengths to ensure that unhappy customers are not disadvantaged/disgruntled/unhappy/outraged.
In most businesses I would suspect that if customers are not happy the owner/management would not only seek to rectify things if they are breaching their 'duty of care' but rather they would go to reasonable lengths to ensure that customers are happy beyond simply 'duty of care'.
Flying F for most is a once in a lifetime thing; could have taken years to save the points, or several months to save the cash, etc. Maybe it's laughable to some that people would complain they are flying an inferior First class product and yes, first world problem sure, but still a problem and such a passenger would be outraged as effectively they are not getting what they paid for. You paid for a flight in F on the A380 not a flight in F on a 747.
For the customer that doesn't care - that's great !
But for those that only flew QF because they "knew" they were getting a flatbed, or for those that spent more money to fly QF cf other airlines and decided it was worthwhile because of the flatbed, or chose QF to "experience" an A380, if such passengers are not happy with the aircraft change then I think QF should accomodate this.
And judging from serfty's reply, they have been, which is pleasing to see