Commercial cancellations, especially short-term ones, tend to be a no-no for two reasons:
- EU261 liability (unless the payout << the likely loss from operating the flight)
- (if they happen with any regularity) the big flashing red neon sign which appears in every time-sensitive (=high-yield) passenger's mind: "This airline is not to be trusted to get me to my important meeting" and which is very hard to eradicate. In general, significant numbers of short-term commercial cancellations are often a harbinger of failure of either the route or the airline.
I have never heard of an "IATA rule" about these and can't even imagine how this would work.