Originally Posted by
andset1191
Very unusual - only during irregular operations when slots are limited.
BAA operates (or used to operate) as use it or lose it slot policy which meant that flights had to actually use their slots 90% of the time or lost the slot, which also reduces consolidation.
Not on a one-off cancellation basis though. If a flight is cancelled (for any reason) the airline doesn't then permanently lose that slot for good.
I think the OP was talking about one-off or occasional consolidations due to light loads. The threat of losing a slot would not come into the decision of airline in this case.