Unlock Xelphatol Spring Water with achievements?

Mine company is Maelstrom.

But, I tried buy Xelphatol Spring Water from NPC vendor.
It's locked. Which achievement I need unlock it?

Thanks

You need to be a Captain. Complete five unique command missions to unlock a squadron mission (Flagged Mission: Sapper Strike) that will promote you once competed.

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Quote:

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Originally Posted by Vnolan

Complete five unique command missions to unlock a squadron mission (Flagged Mission: Sapper Strike).

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If you have any other Flagged Missions do those to.