When AirAsia, IndiGo flights came shockingly close to each other
AirAsia India's Ahmedabad-Chennai flight and IndiGo's Bengaluru-Vadodara flight came within eight kilometers 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.
AirAsia India flight was on a different route than usual
Another probable cause was that the situation was evaluated by the Mumbai airport controller "under the influence of preconceived mind," it said. The report said that most of the flights that go from Ahmedabad to southern India overfly Bhavnagar. However, on January 29, the AirAsia India flight was on a route that is usually taken by planes descending to land at the Mumbai airport.
Both aircraft became reciprocal to each other at different altitudes
Due to the change in routing by AirAsia India flight and "direct routing" of the IndiGo flight that was coming from the opposite direction, the "heading of both aircraft became reciprocal to each other" but at different altitudes, it mentioned. At this time, when there was enough lateral separation, the automation system of the air traffic controller issued a "predicted conflict warning."
Controller did not respond to the 'visual predicted conflict warning'
However, the controller did not respond to the visual "predicted conflict warning," the report stated. The controller presumed that the AirAsia India flight was following its usual route over Bhavnagar due to his or her previous experience. Therefore, the controller perceived that the AirAsia India flight is not in the immediate vicinity of the IndiGo flight, it said.
AirAsia was at 38,396 feet when conflicting traffic was resolved
By the time the controller realized the situation, the Air Asia India flight had reached 38,008 ft while the IndiGo flight was flying at 38,000 ft. The AirAsia India flight continued its ascent as its traffic collision avoidance system (TCAS) issued a warning to the pilots, it said. "AirAsia India flight was at 38,396 feet when the conflicting traffic was resolved," the report added.
Corrective training may be imparted to the controller: Report
"It recommended that suitable corrective training may be imparted to the controller with an emphasis on situational awareness and the importance of warnings generated on the automation system," the report stated.