Does someone know why Cathay Pacific and other airlines use different codes for airplanes than what Boeing has listed? For example they list a 777-367 which seems to be a variant of the 777-300 but I can’t find any information on what makes it a 367 vs a 300. Is that just the code that CX uses for the 777-300s they own? I also notice they have odd ones like A321-251NX, A330-343X and such. So what do those non-normal model numbers mean?
In the case of Boeing, the last 2 numbers are the customer code and it indicates the airline that placed the original order for that particular aircraft. This number does not change and follows the aircraft even after it is sold. Cathay Pacific’s Boeing customer code is 67, so that explains the 777-367 designation. So for example if Cathay Pacific bought a 777-300 from American Airlines, and American had bought that aircraft directly from Boeing…it would be a 777-323 after Cathay acquired it, because that “23” is American’s Boeing customer code.
Regardless of the customer code, it is still referred to in the industry as a 777-300.
Newer Boeing planes like the 777X, 787, 747-8, 737 MAX series do not use the customer code system on their designation. This article may help.
https://en.m.wikipedia.org/wiki/List_of_Boeing_customer_codes
As for Airbus, I believe the number behind the series represents the engine option installed for that aircraft, i’m not 100% sure however.