An OSD advising "AIR FILTER CLEANING" is displayed. Where is the air filter and what is the best method of cleaning?

I checked the owner's manual and it simply tells you to consult your nearest dealer. Haha.

There's this other post here: https://www.askmehelpdesk.com/home-electronics/panasonic-hdtv-air-filter-cleaning-351338.html

That might give you some insight.