AirAsia India's Ahmedabad-Chennai flight and IndiGo's Bengaluru-Vadodara flight came within 8 km of each other with 300 ft vertical separation between them over Mumbai airspace on January 29, according to an Aircraft Accident Investigation Bureau (AAIB) report.

The probable cause for this "serious incident" was the air traffic controller's "loss of situational awareness", the report released earlier this month said. Another probable cause was that the situation was evaluated by the controller at the Mumbai airport "under the influence of preconceived mind", it said.