Seems to drop off the giants in the Desert on their Rare drop table (only seen it drop twice out of at least 50 kills in the desert, never seen it drop anywhere else).
Definitely an upgrade for a lot of people. Decent stats, and the face slot is one that gets neglected by a lot of people due to the relative lack of decent face slot items out there. First time I saw this drop (and I won the roll), it was an absolute flood of rolls from practically every class that could use it, and a lot of these people have been doing Tier 2 Planes for a very long time.