A mid-air mishap was averted in the Dhaka airspace after an automatically generated warning alerted the pilots of IndiGo and Air Deccan planes, which came dangerously close to each other, allegedly breaching the mandatory separation limit, sources said.
The incident, which took place on May 2 in the Bangladesh airspace, happened when IndiGo's Agartala-bound flight 6E892 from Kolkata and Air Deccan's flight DN 602, which was on its way to Kolkata from Agartala, they said.
The incident has been treated as "serious" as IndiGo Airbus A320 plane and Air Deccan's Beechcraft 1900D were just about 700 meters away from each other and is being probed by the Aircraft Accident Investigation Bureau (AAIB), they added.
"The Air Deccan flight DN 602 was on the descend to Agartala from 9,000 feet flight level, while the IndiGo flight 6E 892 was on the climb after taking off from Kolkata for Agartala. It was, however, told to maintain 8,300 feet flight level, which triggered TCAS and forced the two pilots to steer their planes to a safer distance," the sources said.
TCAS is onboard equipment that alerts pilots about the traffic in the proximity of the aircraft and also instructs them about the avoidance action (resolution advisory) to maintain the desired separation between two aircraft.
An IndiGo spokesperson confirmed the incident and said that the matter is being probed by the regulator.
"IndiGo flight 6E-892 (CCU-IXA) operated by VT-IDQ aircraft was involved in RA (resolution advisory) incident with a non-scheduled operator, on May 2, while descending for landing at Agartala," an IndiGo spokesperson said.
IndiGo aircraft was at the prescribed air level, the statement said, adding the IndiGo pilot followed the standard operating procedures (SOPs) and reported the matter to Agartala ATC and the company.
The matter has also been reported to the regulator and is being investigated, the IndiGo statement said.
When contacted, a senior Air Deccan official said that the incident of "airprox" is under investigation.
Airprox is an unplanned event in which two aircrafts come close to each other breaching the standard separation distance.