What are "squawk" codes used for in aviation?

Squawk codes are a key part of the air traffic control system and are primarily used to assign unique identification numbers to aircraft. Each aircraft is assigned a specific squawk code, which serves as a means for air traffic controllers to communicate with and track individual flights on radar. This code is entered into the aircraft's transponder, allowing the aircraft's position and altitude to be displayed on air traffic control screens.

The unique squawk codes help differentiate between multiple aircraft that may be flying within the same airspace, ensuring safe navigation and communication. This is crucial for maintaining situational awareness among pilots and controllers, especially in busy air traffic environments. The other options presented—identifying weather patterns, monitoring flight path deviations, and controlling surface movement—although relevant to aviation operations, do not accurately describe the primary purpose of squawk codes.