Like Vivisteiner, this is a vague rememberance of what's required:

There's this little kid, in the aerodromes, with his parents who keeps spotting Deathgaze. Each time you disembark from an airship, talk to him again, and when he mentions he saw Deathgaze really close, take another airship trip to somewhere, and midflight, go up onto the skydeck thingy, and you should run into Deathgaze then.