I just tried it for an airport code (PDT) and I got the same old error message on regular search.
Also tried advanced search for PHL on NW WP forum and got:
The search term you specified (PHL) is under the minimum word length (4) and therefore will not be found. Please make this term longer.
If this term contains a wildcard, please make this term more specific.
Edit: Since I'm able to post this, I was obviously signed in.