Automatic Dependent Surveillance - Broadcast (ADS-B) is gaining acceptance around the world as the next-generation surveillance technology. It can provide surveillance to air traffic controllers to support today's procedures as well as surveillance in the cockpit to support air-to-air applications. Pilots and ground personnel have begun to benefit from this technology but further benefits from technological improvements can still be realized. These improvements include security, increased data capacity, and advanced applications (4D trajectory and data exchange). To this end research is currently being performed by Sensis Corporation in cooperation with NASA Glenn Research Center to provide enhancements to the ADS-B UAT (Universal Access Transceiver) data link. The research goal is to encourage user acceptance by improving upon existing capability and usability along with providing a roadmap and demonstrations of future data link capability.