D4 class

The D4 class was a type of small Klingon patrol ship used by the Klingon Empire in the alternate reality in the mid 23rd century. 

Specifications
The D4 class was armed with two directed energy cannons on top of the wings near the fuselage. The homing green energy blasts from the cannons could arc through the air before impacting a target. The engine had a single aft exhaust. The wings could be angled in various ways, giving the ship high-speed atmospheric maneuvering capabilities and allowing it to maneuver through tight spaces. The ship had landing capabilities. Troops from the ship could also be deployed on cables mid-flight from four hatches in the underside of the craft. 

History
In 2259, three of these vessels intercepted the K'normian trading ship that was confiscated by the crew of the USS Enterprise (alternate reality) during the Mudd Incident. The trade ship was carrying, , , and another security officer over the Ketha Province on Qo'noS. The D4 class ships forced the trade ship to land. The ships were later destroyed by. 

Background information
Concept artist James Clyne designed the original sketch for the D4 class Klingon fighter. Pixomondo heavily detailed the industrial-type fighter ship design and gave it a "Bird-of-Prey" feel. Visual effects supervisor Ben Grossmann has stated that the ship was designed “''..not in the traditional namesake of the Klingon Empire, but more of like, you can imagine this chase scene as an unarmed trade ship and a bad-ass predator. You had this larger more predatory hawk chasing a little sparrow trying to take advantage of its size and move through little cracks and nooks and crannies and be a little more nimble.''”

In, Vorok's battle cruiser was originally designed by John Eaves to be a prime universe counterpart D4 class starship. However, the K't'inga-class CGI model was reused to represent the ship when it appeared in the episode.

Apocrypha
According to the novelization of the film, the D4 was a “Bird-of-Prey” scout ship and a patrol vessel.

A Klingon starship with identical hull configuration, but much larger, closer to the size of the, appeared in Countdown to Darkness, Issue 4.

Hot Wheels released a miniature of the D4 class in and identified it as a "Klingon Bird-of-Prey".