Voyage exclusive crew

<TGE> Darxide

I'm sure this has been asked and answered before, but do the one-time exclusive Voyage crew "regenerate" if I airlock one that I get? Or is it just gone forever?

eXo | Cadet Matt

I was going to post that "he's gone" Keyser Soze GIF, but then I was like, "Oh. Spacey. No good."
Currently, they are one-time drops. My understanding is that once they drop they will not do so again, regardless if you've airlocked them or not.