Historically, Air China planes flying between mainland China and Taiwan have not displayed the five-star red flag.
This unusual detail stems from political nuances in the relations between the straits. When direct flights between mainland China and Taiwan resumed in December 2008, the parties agreed on special conditions to avoid unnecessary political symbolism.
As a result, some of the aircraft (A330 and A320 models) operating on these routes retain Air China's distinctive design and the phoenix design on the tail, but the five-star red flag - usually displayed on the front of the fuselage - is missing.
It is important to note that this was not a redesign of the entire fleet. Air China still displays the national flag on most of its planes, which fly to a wide range of destinations, including domestic flights. At the same time, non-flag passenger planes are also used on various lines.
It's an interesting example of how political considerations can influence even the smallest details of airline operations and aircraft design.