Interception of Aircraft and Instructions to Land

The interception of an aircraft refers to the act of one aircraft (usually a military or law enforcement aircraft) approaching and flying in close proximity to another aircraft, typically to identify, investigate, or escort it. Aircraft interceptions are carried out for various reasons to ensure aviation security, enforce airspace restrictions, or respond to potential threats.

Unidentified Aircraft: When an aircraft enters restricted or sensitive airspace without proper identification or communication, military or law enforcement aircraft may be tasked with intercepting it to investigate and ascertain its intentions.
Communication Failure: If a civil aircraft experiences a communication failure and is unable to establish contact with air traffic control, nearby military aircraft may be dispatched to intercept and visually communicate with the crew to provide assistance or escort them to a suitable airport.
Violation of Airspace: If an aircraft violates a country’s airspace without authorization, interceptor aircraft may be deployed to monitor, warn, or force the violating aircraft to change its course or land.
Aviation Security: In the interest of national security, military aircraft may be tasked with escorting high-value or sensitive flights, such as heads of state or special cargo transports, to ensure their safety and prevent unauthorized access.

It’s important to note that aircraft interceptions are typically carried out by trained professionals, and international protocols are followed to ensure safe and non-confrontational encounters. Interceptor aircraft usually communicate their intentions to the intercepted aircraft using internationally recognized visual signals and radio frequencies. The goal is to resolve the situation peacefully and ensure the safety of both the intercepted and the intercepting aircraft. The intercepted aircraft is expected to comply with the instructions given by the intercepting aircraft or air traffic control to resolve the situation in a safe and cooperative manner.

Interception Procedures

An aircraft which is intercepted by another aircraft shall immediately:

follow the instructions given by the intercepting aircraft, interpreting and responding to visual signals
notify, if possible, the appropriate air traffic services unit;
attempt to establish radio communication with the intercepting aircraft or with the appropriate intercept control unit by making a general call on aeronautical emergency frequency 121.5 MHz and repeating this call on emergency frequency 243.0 MHz, if practicable giving the identity and position of the aircraft and the nature of the flight; and
if equipped with a transponder, select Mode A Code 7700, unless otherwise instructed by the appropriate air traffic services unit.

If any instructions received by radio from any sources conflict with those given by the intercepting aircraft by visual or radio signals, the intercepted aircraft shall request immediate clarification while continuing to comply with the instructions given by the intercepting aircraft.

Signals

References

AIM SAR 4.4 Radar Alerting Manoeuvres
AIM SAR 4.6 Interception Procedures
CAR 602.144 Interception Signals, Interception of Aircraft and Instructions to Land