One of these craft, the Aeon was inadvertently acquired by a 20th century Human named Henry Starling. Starling found the craft in the High Sierras on Earth, as Captain Braxton, the ship's original commander, had to transport out before the ship crashed. Starling went on to use the future technology found aboard the ship to advance the computer age on Earth by several decades, and create Chronowerx Industries. (VOY: "Future's End", "Future's End, Part II")
The Aeon-type was essentially a small one pilot craft equipped with a form of temporal drive that utilized rifts in the space-time continuum to travel through time. The timeship generated temporal rifts by initiating a temporal inversion from its temporal navigation system, an act which had the effect of powering the ship's temporal field generator. Once the ship's temporal core reached cascade potential, it was possible to open a rift to a specified time and place. The Aeon-type was armed with a subatomic disruptor energy weapon capable of breaking apart the molecular structure of its target. USS Voyager discovered that 24th century phaser fire had little-to-no effect. It also possessed the ability to travel at "regular" warp speeds as well, and was equipped with hyper-impulse drive. (VOY: "Future's End", "Future's End, Part II")
Background information Edit
The Aeon was described as a "vessel", in the final draft of the "Future's End" script, dated 5 August 1996, that appeared as "a sleek, black, thing triangle, half the size of a shuttle. It looks like a curved, obsidian spear-head – small but striking."