Noticed this while doing my dailies in Icecrown, as most of you already know when the Skybreaker and Orgrim's Hammer fly near eachother they begin shooting at the other ship. But it looks like the horde gunners need to get their vision checked:
Followed these as far as I could (they move faster than my mount) and they went all the way to the ocean south of dragonblight before dissappearing into thin air!