Keller hatches a plan to create a resonance reversal using the prototype displacement beacon in the Gamma Labs. However, he needs a satellite in orbit before he can go through with the plan. Personnel in the High Altitude Launch Center are ready to launch the satellite, but due to a military air traffic lockdown that is in effect they can not. To remove the lockdown, an all-clear code is needed. Keller, Green, and Cross use the transit system to get to the nearby Level 3 Dormitories. There, they begin searching for a security guard with the codes. Their task is made more difficult by the fact that HECU soldiers are also present, and are busy eliminating science and security personnel. Eventually, the security guard is found. Armed with the codes, Cross, Green, and Keller travel to the Black Mesa Air-Traffic Control facility on the surface.