Civil and Military air traffic control (ATC) systems rely on three core technologies, satellite positioning systems ,radar, and communications (data and voice), to safely manage the congested airspace across the globe.  Due to the density of traffic, and the increased safety risks presented by takeoff and landing, higher resolution and faster update systems are required near airports. Precision frequency and time control is a critical element for all three of these technologies.  Many of these systems are receiving critical upgrades due to the aged infrastructure. This presentation will discuss how various traffic control systems work, and the role and requirements of frequency and time in these systems, including ATC radars, Automatic Dependent Surveillance Broadcast (ADS-B), Wide Area and Local Area Multilateration (WAM/LAM), Satellite Augmentation Based Systems (SBAS), and data and voice communication systems.  Timing architectures solutions that plan for GNSS denial will be presented.