All,

 

Thought I'd share this with you. I was messing around in a Beech 18 I had just downloaded when I saw the AI aircraft text over a Bahamian island. I flew over to investigate, only to find that there was no plane under the text. It simply says "avenger". The "airplane" flies at night and can be found at the MYXB airport. Has the mystery of Flight 19 been solved?

Sounds like you must have installed Bill Lyons' Grumman Goose package at some point. He included the "invisible" Flight 19 avengers so you would hear them talking to ATC, but not be able to locate them visually. Just like the real Flight 19.