From Star Trek: Theurgy Wiki
In 2368, the Hornet joined Captain Jean-Luc Picard's fleet that blockaded the Klingon-Romulan border during the Klingon Civil War. The ship was one of twenty-three assembled for the fleet and was one of the seventeen chosen for the tachyon detection grid network.
During the years of 2368 and 2369, the Hornet was modified to serve as a carrier. During 2370 and 2371 the retrofit carrier underwent a training shakedown cruise of also doubled as wartime combat drills in Sector 001. The mission also included secret visits to other Federation worlds, where the Hornet’s fighters were exposed several harsh alien environments to test their endurances and ensure that their pilots were could survive any climate. The instructors included Captain Solok of Vulcan, and Captain Xan of Andoria, and simulated Jem'Hadar and Cardassian battles and dogfights were tested during this training tour.
Leon Marquez served aboard the Hornet for five years from 2371 until 2375, being promoted from lieutenant (senior grade) to lieutenant commander in 2375. During this time the Hornet was commanded by Captain Xan, Marquez’s former commanding officer from the USS Nautilus. Commander Al'Fadil was the ships executive officer who often served as acting CONN officer during those years. Also serving aboard the Hornet was Xan’s daughter Warrant Officer Tarsi who served in the ship’s tactical department before transferring to sciences. Marquez served as the ship’s chief tactical officer after 2373 before being promoted to lieutenant commander and briefly serving as executive officer in 2375.
Native of Denobula and former constable Klex Sonden transferred from the security to the tactical department when he was assigned to the Hornet in January of 2371. He worked his way up the enlisted ranks and remained aboard the Hornet before transferring to the USS Resolve in 2378.
During the Klingon-Cardassian conflict of 2372, Captain Xan was injured during in an attack, but Marquez stayed with his mentor, engaging him into such an argument which actually wound up saving the old Andorian's life. The precise remark had something to do with going out with the Captain's daughter. It earned him a promotion, but also, allegedly, an ushaan challenge. Of course, Marquez turned out to be bluffing; something Marquez learned how to emulate from his mentor during their long friendship.
James Mariner spent his cadet cruise aboard the Hornet, joining the crew as a cadet in 2373 before being promoted to ensign in 2375. During this time he displayed courage, cunning, and initiative but lacked discipline. He remained aboard the Hornet as a security officer before transferring to the USS Resolve in 2378.
During 2375, Captain Xan had been forced to use non-security personnel as supplementary reinforcements for ground engagements. Many of the fighter pilots would often go months without seeing the inside of their fighters’ cockpits when the Hornet was forced to reinforce planetary defenses in the Alpha Quadrant. Lieutenant Commander Marquez, the Hornet’s chief tactical officer, had the dubious distinction of being highest-ranking officer left in the Battle of Serenity Valley on HT-997, a battle that was fought on an obscure rogue planet whose only real value was its location and the possibility to install a remote sensor array.
During the Battle of Serenity Valley on HT-997, Captain Xan's orders were to hold the planetoid. Lieutenant Commander Marquez, helped coordinate the planetoid's defense. In summary, the battle was an absolute success, though the time eventually came when Marquez was shot down behind enemy lines. Thanks to his appropriated Jem'Hadar rifle and survival instinct, Marquez was able to cause havoc behind Jem'Hadar lines, picking off units hiding behind cover assuming they were safe. It was a particularly bitter experience for Leon Marquez, now killing people instead of starships.
During the events of Starfleet’s Operation Return, Captain Xan lost an antenna forcing him to bark orders at the bridge from sickbay. Commander Al'Fadil surrendered the helm position to Marquez and took the captain’s chair and Tarsi replaced Marquez at tactical. After the battle, most of the Hornet’s senior officers including Marquez were awarded the Starfleet Medal of Commendation.
After the conclusion of Operation Return, Commander Al'Fadil was transferred off the ship and Lieutenant Commander Marquez was appointed the Hornet’s executive officer. The ship received the Scorpion-class Attack Fighter.
In 2375, the Hornet put in for repairs at Deep Space 9. However, in order to bring forward repairs of the Romulan warbirds Dividices and Genorex, the Hornet, as well as the IKS Rotarran, had to stand by. (DS9|Inter Arma Enim Silent Leges)
Before the Dominion War was over the USS Hornet was forced to evacuate to its battle bridge. Many of her crew, including the flight crew were killed in action, making the victory at the end of the war a solemn one.
When the war ended, Captain Xan was removed from command for allowing the Romulan flagship to be destroyed in the Battle of Cardassia. An inquiry later revealed that the Romulan Admiral serving aboard the flagship had taunted Xan about the death of the Andorian's daughter during the Hornet’s stopover at Deep Space 9.
The ship's registry appeared in the okudagram depicting the tachyon detection network in "Redemption II". According to the Star Trek Encyclopedia (3rd ed. p. 196), the class of this starship was Renaissance. In the first edition of the Star Trek Encyclopedia (p. 320), it was mistakenly stated that the registry of this ship was NCC-10523.
According to the Star Trek Encyclopedia (3rd ed., p. 196), the ship was "named for an American aircraft carrier that fought at the Battle of Midway in World War II. Years later, another ship with that name was the recovery vessel for the Apollo 11 moon landing mission."
Purposely, the producers had Starfleet's Hornet serve alongside USS Akagi (named after a Japanese carrier that fought against the real life Hornet at Midway) in "Redemption II" – episode Writer Ronald D. Moore thought it fitting that, in a future where Humanity had become united by its own accord, ships whose namesakes had fought one another would now fight side-by-side. (Star Trek Encyclopedia, 3rd ed., p. 4)
According to the Star Fleet Technical Manual, there was a Constitution-class USS Hornet in service in the 23rd century with the registry NCC-1714 (although the game supplement Federation Ship Recognition Manual gives its as registry NCC-1778). This would seem to be the same Hornet that was mentioned as a combatant in the novel Dreadnought!.