The Transit over the centuries has been considered a House Liao design, but the fall of Tikonov during the Fourth Succession War resulted in the design being fielded by the Federated Commonwealth. The recovery of Star League technology did not result in any upgrades to this design since the Commonwealth placed more importance on BattleMechs though. The advent of WarShips forced the AFFC reconsider this stance and they began putting resources into upgrading the existing AeroSpace forces.
                 The upgraded Transits served on both sides of the FedCom Civil War, where MechWarriors learned to fear the approach of their distinctive silhouette. The survivors of the Civil War also fought during the Jihad, though no replacements or spare parts came out of the Syrtis Federation and their numbers declined rapidly due to battle losses. When the Ridzik brothers captured the world, they placed a priority on replacing their rag-tag AeroSpace forces with as many Transits as the factories could build, and lines have been running constantly since.

         While not much faster than House Liao's heavy fighter, the Transgressor, the Transit is one of the more potent medium-weight aerospace fighters in the Human Sphere because of its armor placement and durability. Powered by the Rawlings 200 fusion engine, it can generate all the energy that its four Intek Extended-Range Medium Lasers need, though normally they are fired simultaneously. The nose-mounted Imperator rapid autocannon is especially effective against DropShips and BattleMechs, but its potential for heat buildup can cause problems if used at full fire rate with the lasers.
         Though its armor is not the strongest among medium aerospace fighters, the Transit has proven sufficiently well armored during most extra-atmospheric firefights. Its staying power against comparable fighters has also been exemplary. When set upon by heavier fighters, however, it runs into trouble if it cannot generate a killing shot early.
         One complaint many fighter pilots make about the Transit is that it offers a far larger target than other medium fighters. Many pilots feel that the designers would have done better to create a more compact design. The designers argue that the Transit's large wing surfaces and control points make it one of the more space and airworthy fighter craft in the Human Sphere. The fighter is remarkably easy to fly, and uncontrolled maneuvers are very rare. According to many pilots, however, control is less important than speed and agility.

         A fair number of TR-12Ds still exist in the Lyran Commonwealth, most in the service of rich nobles that can afford to keep the main cannon operational. Due to breakdowns in the advanced construction, the vast majority of those in use in the Federated Suns have long since failed. Most TR-12Ds in existance serve the militaries of the Syrtis Federation and the Tikonov Free Republic, where they are a common sight.