No, but they provide the best efficiency/performance for the buck. China can produce its own jet turbines, but they have to trade off performance or longevity to do it.

Interesting. Thanks.

Don't forget GE Aerospace. It gets a bit weirder too since you have joint ventures like CFM and Engine Alliance.

Good point. Isn’t there also Safran?

Yes. Their engines are mostly for military applications, tough, so they are less well known of the general public. Other than that, they are half of CFM International, but again they are not very visible.

They don't make them end to end either. Their jet engines are made up of parts supplied by thousands of suppliers.

Obviously, but I would imagine that most of the “magic” isn’t in the supplied components, but in the finished product. Otherwise reproduction would be easier.