Explainer: What is the IAF’s role in assisting civilian flights in distress

On May 21, an Indigo Airlines flight from Delhi to Srinagar with 227 passengers and crew on board encountered severe weather and heavy turbulence near Pathankot, which rendered some critical instruments non-functional and damaged the airframe.

Despite the emergency situation, the flight was denied permission by the Lahore Air Traffic Control to enter Pakistani airspace to skirt the rough patch. A NOTAM (Notice to Airmen) stating that Pakistani airspace was not available to Indian aircraft was cited as the reason.

How the IAF helped

With the onboard sensors that indicate speed and altitude not functioning, the autopilot disabled and warning alarms sounding in the cockpit, the Indian Air Force controllers on ground provided the Indigo pilots with crucial flight data using their own radar systems.

The IAF’s Northern Area Control had advised the Indigo crew about the NOTAM, which is a regular feature in charting flight routes by all airlines to ensure safety of the aircraft and the passengers.

It also assisted the crew in coordinating their proposed flight diversion by contacting Delhi Area, which was the authority for according clearance, and also passed the requisite contact frequencies of Lahore for weather diversion request.

“Once Lahore refused overflight clearance and the aircraft proceeded towards Srinagar, the flight was subsequently professionally assisted till a safe landing at Srinagar airfield by giving control vectors and groundspeed readouts,” an IAF officer said.

Monitoring role 

The IAF is responsible for the defence of Indian airspace and all aircraft operating within Indian-controlled airspace, including medical evacuation and drones, require air defence clearance and are allocated a particular radio communication frequency and call sign.

All flight plans filed by civilian operators are passed on to the IAF, which maintains a constant watch on the skies through a network of radars and electronic sensors. The efficacy of its surveillance was witnessed recently during Operation Sindoor, when Pakistani missiles, rockets and drones targeting Indian installations were intercepted effectively.

Before operating a flight, the crew is required to file a flight plan at the station of the flight’s origin with the civilian regulator, the Directorate General of Civil Aviation (DGCA), though the Airports Authority of India (AAI). This can also be done online. For unscheduled foreign flights destined for India, it is required to be filed several days in advance.

A copy is routed to the defence authorities also. In India, every major civilian airport has a military liaison office.

Clearing the flight plan

The flight plan contains details like identification, the way points en route, that is the reporting points and places where course is to be altered, altitude, estimated time of arrival, call signs, radio frequencies, etc.

After the flight plan is approved, the flight is allocated two numbers, one by the civil regulator and the other by the defence authorities.

This information is also passed on to the air defence network. The aircrew is required to have all clearances before they are permitted to start the aircraft engines.

The AAI has established a Central Air Traffic Flow Management System to provide support to the Central Command Centre. The system enables AAI and aircraft operators to perform strategic and tactical air traffic management associated with arrivals and departures.

Another online system, Skyflow, provides all stakeholders a common situational awareness of the current air traffic flow management status and flight details.

All civilian flights follow specific routes and operate within designated air corridors. Permission from Air Traffic Control (ATC) is required for any deviation, be it due to weather or some other onboard emergency.

If deviation happens

Unauthorised deviation from the approved course will entail retaliatory action. The crew would be contacted by the ATC over radio intimating of the deviation and asking for correction or an explanation.

It could also lead to a ‘scramble’ by the Air Force fighters to intercept the erring aircraft for a visual inspection, communication or execute a force landing. In extreme circumstances, where no response from the crew of the aircraft is considered a serious threat, it may even be shot down.

En route, all civilian aircraft are required to have the transponder switched on. This beams a constant radio signal identifying it and relaying its position in the air.

When in the air, the aircrew is required to report their position to the ATC when passing over designated points as mentioned in the flight plan, or when entering the airspace of a foreign country.

This keeps a track of the aircraft’s movement and in case of any delays or changes in the time schedule, enables ATC to manage air traffic and issue the necessary advisory to other aircraft in the vicinity.

All this while, the overhead civilian traffic is also tracked by the Air Force and radio communications are monitored. All radio communication is on open frequencies, which are different from those used by the military.

The IAF collaborates with the DGCA and the AAI in managing airspace and controlling air traffic. Many defence airbases in India have a civil enclave, where the primary facilities like the runway, ATC and emergency services are owned and operated by the Air Force. A small complex for handling civilian operation is attached to it.

India