Wikipedia (emphasis mine):

When addressing a (male only, unlike in many fictional works) superior (e.g. Officer or Warrant Officer, but—most of the time—not a non-commissioned officer, in the military), “sir” is used to replace his specific rank. However, a United States Marine recruit addresses both commissioned and non-commissioned officers as “sir”, especially drill instructors.

Battlestar Galactica’s use of “sir” to address female pilots or the freaking fracking President kills me. Especially for a sci-fi setting. Which ostensibly places female characters in prominent spots, somewhat emphasizing gender equality. Sir.

(I like “frell” better than “frack,” by the way.)