IAF Embraer 135 Legacy Jet: Sushma Swaraj was flying went incommunicado. Mauritius ATC reported aircraft as missing. AAI indicated that Mauritius ATC might have acted in haste

In what set panic for about 15 minutes, the Mauritius ATC authorities issued alert warning for "missing plane" Minister for External Affairs Sushma Swaraj was flying on Sunday from Delhi to Durban to attend BRICS and IBSA meets during her five-day visit to South Africa.

Minister for External Affairs Sushma Swaraj is in South Africa on a five-day tour to attend the BRICS and IBSA meets. BRICS is an economic bloc comprising Brazil, Russia, India, China and South Africa. IBSA is an India-Brazil-South Africa forum for cooperation on issues of common interests.

On her way to South Africa, Sushma Swaraj had a stopover in Mauritius and in between, the aircraft she was flying went incommunicado -- technically reported missing -- for 14 minutes. This set panic at certain levels that saw people expressing their concerns on social media. However, it was not really a cause of panic considering Sushma Swaraj was flying over international waters.

First, What Exactly Happened?

Sushma Swaraj was flying in an Indian Air Force plane named Meghdoot, an Embraer jet aircraft. Embraer is a Brazilian aerospace company. Swaraj flew in an Embraer 135 of the Legacy series.

These aircraft are powered by two turbofan engines and are not meant for long-haul flights. They require more frequent refuelling. Sushma Swaraj's Delhi to Durban flight had two technical stops at Thiruvananthapuram and Mauritius.

The Embraer 135 Legacy left Thiruvananthapuram at 2.08 pm on Sunday for Mauritius. The next ATC (air traffic control) to communicate with Sushma Swaraj's aircraft was that of Male, the capital of Maldives. The Male ATC reported last contact with Sushma Swaraj's aircraft at 4.44 pm.

The Mauritius ATC could not establish contact with the aircraft crew for the next 14 minutes and this was the period of panic. The Mauritius ATC sounded an alert, technically called "activating INCERFA", which is a code used in international air traffic for uncertainty about an aircraft.

Why INCERFA?

All inland air traffic routes are covered under radar surveillance but those over the high seas are not. High seas don't fall under any country's sovereign jurisdiction and a nation keeping surveillance over these areas may compromise strategic assets of other countries.

This non-radar coverage of the air traffic routes makes aircraft dependent on VHF (very high frequency) or HF (high frequency) radio communications. These are erratic modes of communications. Due to the uncertain nature of VHF or HF communication, the areas under non-radar coverage are also known as dark zones of international air traffic.

After leaving the Male ATC coverage area, Sushma Swaraj's plane was in VHF zone for some time before entering Mauritius ATC space. It took the crew of Embraer 135 Legacy some time after entering Mauritius air space to have ground contact with ATC. By the time the crew got in touch with the Mauritius ATC, that is 4.58 pm, the officials had activated INCERFA.

Responding to INCERFA activation, the Airport Authority of India (AAI) indicated that the Mauritius ATC might have acted in haste considering the high-profile dignitary flying in the aircraft. In its statement, the AAI said that INCERFA is activated after waiting for 30 minutes. The aircraft was incommunicado for 14 minutes in total.

What Is The Standard Protocol?

INCERFA is the first of the three-stage emergency phases of flying, as per the International Civil Aviation Organisation (ICAO). It is a specialised agency of the United Nations to codify the principles and techniques of international air navigation.

The other two phases of air traffic emergency are known by codes, ALERFA and DETRESFA. While INCERFA is an uncertainty phase for an aircraft, ALERFA is the "alert phase" and DETRESFA is the "distress phase" of air navigation.

ALERFA is sounded when there is apprehension about the safety of an aircraft and its occupants. DETRESFA phase refers to a reasonable certainty that an aircraft and its occupants are threatened by grave imminent danger requiring immediate assistance by a rescue team.

As per the standard protocol, INCERFA is activated if contact with the aircraft is lost for 10 minutes while it is flying in areas under ATC control. The time lag is 20 minutes for ALERFA and 30 minutes for DETRESFA in areas under ATC control.

But if the aircraft is flying over areas beyond ATC control, INCERFA is activated only after waiting for 30 minutes after the loss of radio contact. The next alert phases can be upgraded every 30 minutes thereafter.