What is used as the reference line from which aircraft will be evaluated for correlation in corridors?

• A. PID On
• B. IFPID
• C. IFF On / IFF Off
• D. Passive identification on line PIDON

Answer: (D)

The key idea is to have a stable baseline to compare every aircraft against as it moves through the corridor. Using passive identification along the line creates that reference line: you identify and track aircraft using existing, non-intrusive signals as they run along the corridor, and you evaluate each observed track against this fixed line. This provides a consistent frame of reference for correlation, so you can tell whether an aircraft is on the expected path and whether its identity matches what the corridor model predicts.

Other options don’t establish that reference baseline. Simply turning PID on or off isn’t about creating a corridor reference line, IFPID isn’t the mechanism used to define the corridor reference, and IFF toggling changes identity information rather than providing a stable corridor reference for correlation.