AAIB probe reveals alarming details of AirAsia India, IndiGo aircrafts' near-collision

In a significant revelation according to an Aircraft Accident Investigation Bureau (AAIB) report on the near-miss involving AirAsia India's Ahmedabad-Chennai aircraft and IndiGo's Bengaluru-Vadodara flight, the vertical separation between both aircraft was recorded at 6.5 km. Subsequent to a formal probe in the matter, it is now clear that both aircraft in concern came within 8 km of each other, marking 300 feet vertical separation between them over Mumbai airspace on January 29. 

The Air Asia flight was headed to Chennai from Ahmedabad while the IndiGo flight was flying from Bengaluru to Vadodara when the incident occurred over Vapi, Gujarat. Additionally, the IndiGo flight coming in from the south was allowed to fly towards Ankleshwar, Bharuch. Due to a change in routing, both aircraft were flying towards each other, albeit at distinct altitudes.

AirAsia India and IndiGo flights near-miss incident

Elucidating the incident, the AAIB report stated that an aircraft typically crosses Bhavnagar to fly from Ahmedabad to Chennai but the AirAsia flight in question, on January 29, followed a route that is normally taken by aircraft while descending to land in Mumbai. The probable cause for "this serious incident" was the air traffic controller's "loss of situational awareness", the report released earlier in August stated. 

"Another probable cause was that the situation was evaluated by the controller at the Mumbai airport "under the influence of preconceived mind", the report suggested. 

Apparently, an automated system at the Mumbai Air Traffic Control generated a 'predicted conflict warning', which radar failed to respond with relevant syntax. The report indicated inadequate and restricted manpower at the Mumbai air traffic control owing to the COVID-19 pandemic.

By the time the controller responded to the alert, the AirAsia aircraft at 38,008 ft and the IndiGo aircraft at 38,000 ft were closing in proximity. The automated Traffic Collision Advance System (TCAS) in the AirAsia cockpit blared an aural alert, commanding the pilots to climb. As a result, the flight climbed to 38,396 ft, moving safely away from the 38,000 ft altitude that IndiGo was at. 

Final report on AirAsia India & IndiGo flights' incident

Due to a detour by AirAsia India flight and "direct routing" of the IndiGo flight from the opposite direction, "heading of both aircraft became reciprocal to each other" but at different altitudes, the report mentioned.

The report stated that the minimum separation between both aircraft was recorded as 8 km laterally when the vertical separation was 300 ft, with the IndiGo flight flying over the AirAsia aircraft.

Furthermore, the reports suggested a suitable corrective training that may be installed at the controller with a bigger emphasis on situational awareness and the weightage of warnings generated on the automated system.

"It is recommended that Airports Authority of India may reassess the volume of traffic in all sectors which were withdrawn due to less number of traffic during the lockdown and may implement sectors as before pandemic," the AAIB final report stated.