China is projected to be the world’s largest air market within a decade, and has, to this point been one of Boeing’s biggest customers.

Last year they debuted their own narrow body aircraft, with multiple size options, and earlier this year applied for certification for the European market, a process which usually takes years. A request for US approval will happen, although they may be waiting because of the rising trade tensions between China and the US. In any case, it’s inevitable, and likely that with Chinese labor and know how (some of which gained by Boeing being required to produce some components there).

Inevitable, I see a long term decline for Boeing - even if it manages to straighten out its other current and obvious issues (which I’m not sure is likely anyway.)

Here’s an article with a timeline of China’s progress in penetrating - perhaps one day to dominate - another industry:

China’s C919 passenger jet marks first anniversary of commercial flights: 13 key moments from year 1

China’s C919 home-grown, narrowbody passenger jet completed its first commercial flight between Shanghai and Beijing on May 28, 2023

Over the last year, China’s rival for Boeing’s 737 and Airbus’ A320 has made its international debut at the Singapore Airshow and received more domestic orders

The C919 – China’s home-grown, narrowbody passenger jet – is designed to carry between 158 and 192 passengers and compete with Boeing’s 737 and Airbus’ A320.
It is built by the Shanghai-based state-owned Commercial Aircraft Corporation of China (Comac).
The C919 completed its first commercial flight at the end of May 2023 after 15 years of development.
scmp.com - Chinas passenger jet marks first anniversary commercial flights key moments year