> That being said, the probable continued existence of unapproved parts on the market should not really be cause for alarm to the flying public. [...] The fact is that Partnair flight 394 remains the only crash of a commercial airliner linked to unapproved parts, placing the issue rather far down the list of problems that cause the most crashes.
It's worth a read, but the summary is that the problem is mostly under control and unlikely to cause a crash.
> In general, this is because unapproved parts cause annoying breakdowns and increase maintenance costs, but don’t directly cause crashes, simply because there are very few individual parts on an aircraft which could cause a crash if they fail. Redundancy in aircraft design largely shields us from the consequences, with the primary exception being very old aircraft like LN-PAA which predate many modern airworthiness requirements. Even then, it took multiple unapproved parts in multiple locations, plus inadequate inspections and poor documentation, to actually bring down the plane.