(covers information from several alternate timelines)
The Stuka (or Junkers Ju 87) was a dive-bomber airplane used on Earth, by Germany, during World War II. Their standard equipment included sirens used to frighten the enemy during an attack, and an armament of either 7.92 millimeter machine guns, 20 millimeter cannons, or larger, anti-armor, 37 millimeter cannons.
In 1944, when Enterprise was trapped in an alternate timeline, Vosk dispatched a squadron of Stukas refitted with plasma cannons, one of them carrying the registry "A5 CH", to destroy Enterprise in order to prevent it from in turn destroying the temporal conduit the Na'kuhl were constructing. (ENT: "Storm Front, Part II")