Plan 99 was a pre-arranged, pre-defined phrase used as a code by Clone Force 99. It detailed a scenario wherein one member would give up their own life to ensure the squad's survival, specifically when their safety was at risk.
In approximately 18 BBY on the planet Eriadu, during the incident known as the bombing of Raven's Peak, Tech put the plan into action. He sacrificed himself by destroying the hinge connecting the rail car's two sections, causing one section to detach and fall, taking him with it. This action allowed the rest of the squad to escape before the Imperial forces destroyed the entire rail car.
During the conflict on Mount Tantiss, Crosshair suggested he would initiate Plan 99 by entering the facility by himself to locate Omega. His goal was to ensure her safe return and reunion with Hunter and Wrecker. However, Hunter and Wrecker objected to this strategy, and the entire group infiltrated the base together. This collaborative plan proved successful, ultimately freeing them from the Empire's pursuit.