Can you confirm that the little icon to switch the phone off in the controls menu is effecively the airplane mode on the Fenix 5X Plus?
I was trying to find the bluetoth and wifi enable / disable controls. The documentation on the internet said to use this icon but it was missing from the watch.
Eventually I found some options screens to add it back in - I've done that. The docs are a bit confusing, but this seems to be the only way to put the watch in airplane mode?