I don't think it's possible to say. All we know is that fake parts are in circulation.
We can assume some aircraft have fake parts out there, or there wouldn't be a market for them.
But it must be hard to trace fake parts.
We can assume some aircraft have fake parts out there, or there wouldn't be a market for them.
But it must be hard to trace fake parts.
But then again, they also buy direct from factory and keep parts on hand for decades.