What does a transponder help air traffic controllers track?

A transponder is a crucial device in aviation that provides real-time information to air traffic controllers about an aircraft’s location, altitude, and identity. When an aircraft is equipped with a transponder, it communicates with ground-based radar systems. This system works by receiving interrogation signals from the radar and then responding with a burst of data that includes the aircraft’s unique identification code, current altitude, and sometimes additional data like the aircraft's ground speed.

The information transmitted from the transponder allows air traffic controllers to have a clearer picture of the air traffic situation in their jurisdiction, enabling them to manage and direct aircraft safely and efficiently. This capability is essential for maintaining safe separation between aircraft, particularly in busy airspaces.

While other options touch on important elements related to aviation, they do not directly pertain to what a transponder specifically monitors and transmits. Weather patterns, passenger preferences, and cabin pressure systems are managed through different systems and procedures not associated with the primary function of a transponder.