Both tickets are award tickets. CX is an AS award and QF is a BA award.
AS award was booked in March. BA award was booked 5 days ago.

My original hope is that CX would release business class availability HKG-BNE in 7 to 10 days departure time as that is what it normally does on the HKG-Australia award seats based on the CX forum information and my own observation in recent past.
If CX releases the HKG-BNE I would just pay the change fee at USD125 per ticket to change the AS award and cancel the BA award which the cancellation fee is just the cash portion (the taxes) while the Avios go right back to the account, so it is a cheap insurance if CX does not release the desirable seats.

What I did not realize is, CX105 has poor on time performance. That throws a wrench to the current plan.

Here are some contingency plans we are considering...

Option 1) Instead of trying to fly to BNE on the same day, we can do an overnight at MEL, dont even bother to go into town but overnight at the Holiday Inn MEL. Then fly to BNE the next morning.
Would need to book the next morning flight, and cancel the current flight, out the $27 cash payment and one night of hotel at MEL. (The hotel at Brisbane is on a 5th night free award booking, hence it is the same point cost for either 4 nights or 5 nights, cancellation deadline is 6pm hotel time the day before arrival.)

Option 2) Cancel the current 15:40 QF 630, and rebook the 19:10 QF 634 or the 20:10 QF 636. Is this the last flight of the day?
QF 634 has only 3 coach award seats and 1 business award seat available. So if we opt for this we may need to act soon. QF 632 departs at 18:10 has only 1 business seat available.
5 days ago when I booked the QF 630, the availability was 15:40, 16:10 then jumped to 19:10. Yesterday 17:10 shows up with 7 coach seats and 3 business seats but 18:10 only 1 business seat. These 2 departure times were not showing availability 5 days ago. I will keep watching.

Option 1) does not require me to act quickly because every MEL-BNE flight on Nov 9th is wide open on award availability, from 06:10 thru 20:10 every 60 min, BA does not even show how many seats - when it is like that, it means the flight is wide open. Else BA would show how many are available, from 8 down to 1.

This bring up 2 questions on how QF operates -

A) Does QF let you stand by on earlier flight? i.e. if we are booked on the 19:10 flight but arrive much early due to CX105 has minimal delay - Does QF allow us to move up if they have seats on earlier flights?

Virtually all US airlines would let you do this on award tickets. It is advantageous to the airlines that they can move you to otherwise unsold seats thus free up your original seats on the later flight that they may be able to sell or give it to standby passengers.
But foreign airlines seem to be more sticklers to the tickets. I know BA would not budge at all even on BA issued tickets.
Based on some old DPs I found last night, QF seems just as sticky as BA.

B) Does QF allow you to hold 2 reservations on the same day and not automatically cancel 1 of the 2?
AA would do system sweep to cancel a "duplicate" booking of the same itinerary on the same day.
If QF does not cancel "duplicate" bookings (both would be paid for), then I have better flexibility thanks to they are BA awards which are being very reasonably priced.

Thoughts and suggestions are very much appreciated!
[MENTION=152195]vbroucek[/MENTION]

Thanks for sharing your data point. I hadn't thought about that. But if we check in online it would be at the HKG CX lounge when we know better about the flight departure time. I am not sure if the CX105 has wifi onboard. If it does, we can do OLCI while in flight. Though I believe CX has not had wifi fleetwide.

[MENTION=6129]Mwenenzi[/MENTION]

Unfortunately credit card trip interruption coverage only cover expenses already incurred but not subsequent new cost. In the case of CX significant delay, the subsequent new cost of getting new tickets are unfortunately not covered.