I’m wondering if maybe one of the system options, specifically the UTF-8 beta, could help because I remember that there used to be a problem where no matter what you selected in MSFS, after a restart you always got the same airport and airplane.
Try.
1 Exit MSFS.
2 Go to
C:\Users\YourUserName\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\MISSIONS\Custom
3 Delete folder named CustomFlight
4 Install English (United States) language pack
5 Make sure to enable the Beta: Use Unicode UTF-8 for worldwide language support option.
Go to Windows settings > time & language > language & region > administrative language settings. Click > change system locale and check Beta: Use Unicode UTF-8 for worldwide language support.
Click ok and restart PC.