Ooh, I learned a new key and a new word today. 
It sounds like you use it similar to the indoor=* key. If so, you might as well use it for hallway corridors as well as POIs. At some airports, the terminals are connected only before security, while at others, they’re connected only after security.
Lately, I’ve been using access=permit permit=boarding_pass for this purpose. Iterative refinement of access=permit works more generally for any security-controlled facility, such as stadiums and courthouses. When you’re out on the town and hungry for a Big Mac, the last thing you want is to be directed to an airport or stadium concessionaire. This also allows me to distinguish between passenger and staff areas that are both past security.
amenity=lounge has good documentation and even an (abandoned) proposal. There are a number of airport lounge chains that aren’t in the name suggestion index yet because amenity=lounge and public_transport=lounge were roughly neck-and-neck the last time we looked into it, but the situation seems to have changed in favor of amenity=lounge.