In addition to mode C functions, what extra capability does a mode S transponder provide?

A mode S transponder provides several advanced capabilities beyond those offered by mode C transponders, one of which is the ability to support data link communications. This feature allows for the transmission of information between aircraft and air traffic control, greatly enhancing communication and operational efficiency.

Mode S transponders also facilitate mid-air collision avoidance by participating in the Traffic Alert and Collision Avoidance System (TCAS). This system uses the information from mode S transponders to detect potential collisions between aircraft and provide alerts to pilots, ensuring improved safety in the skies.

While the other options may seem relevant, they do not directly relate to the specific extra capabilities of mode S transponders. Database of air traffic control regulations, real-time weather updates, and mid-air collision avoidance are not features provided by the mode S transponder itself, but rather involve different systems and methods of operational safety. In contrast, the data link communications aspect is integral to the enhanced functionality of mode S, which equips it with the tools to greatly improve situational awareness and aircraft-to-aircraft communication.