Originally Posted by
Dave Noble
LHR-SYD bookings have their own inventory , since LHR-SYD is a direct sector in its own right
LHR-SIN, SIN-SYD and LHR-SYD all are separate availabilities
As long as changes are permitted and any change fee applies, should be ok to book the next day as long as BA releases award seats for SIN-SYD
SIN-SYD gets its own inventory but we don’t reallly know if BA make 2J available on it systematically, alongside the 2J LON-SYD that do appear.
Route changes aren’t normally permitted if the new route has a different avios cost - that’s the overriding problem. You couldn’t normally change from LON-SYD to LON-SIN-SYD as a topical example. You can’t add a return either normally, but there’s an exception in place for T-355 241 bookings ... which might very-optimistically extend to something that can help the OP here.