How does an aircraft transponder respond to an interrogator's query?

An aircraft transponder responds automatically to an interrogator's query. When the transponder receives a signal from an air traffic control radar system, it is designed to immediately transmit its identification and altitude information back to the interrogator. This automatic response is critical for maintaining situational awareness in the airspace, as it enables air traffic controllers to track and communicate with aircraft without any manual input from the pilots.

The use of automatic transponder systems enhances safety and efficiency in air traffic management, as pilots do not need to take additional steps to relay vital information. It allows for a quick and effective means of identifying aircraft, especially in busy airspace.

In contrast, manual responses, delayed responses, or responses prompted by the pilot would not meet the operational requirements of real-time communication and aircraft identification needed in flight operations, especially under busy air traffic control conditions.