Cygnus subclass

The Cygnus subclass was a class of Federation starship in operation during the 23rd century, the third batch of Hermes class starships built. Unlike its Hermes and Monoceros class predecessors, the Cygnus was specially outfitted to serve as a diplomatic and command courier

Like the Hermes, the Cygnus consisted of a saucer section and nacelle, each similar in exterior design to that of a vessel of the 2260s. Its configuration was significantly different, however, employing only a single nacelle.

In the late 23rd century, like the Constitution class, these old workhorses received major overhauls in hull and warp designs.

Background
The Cygnus-class starship was a design originally created by Franz Joseph in his Star Fleet Technical Manual.

According to the Star Fleet Technical Manual, the Cygnus was designed to serve in a diplomatic/command courier role.

The class may have been named for the constellation Cygnus, as all the named ships of that class appear to be named for constellations representing birds.