I totally agree, visibility of distant air objects need some tweaking. But as I wrote elsewhere, adjustement of icons/labels in labels.lua can be a temporary solution for WWII combat, where the whole situational awareness depends on your Mk1 Eyeball...
Check this out:
This is not ideal solution because the dot/label is not scalable, it has the same size at 8 km away as well as in front of your prop...