Two IndiGo planes came dangerously close over Delhi airport in November. Then…

As per the report, the A321 departed at 12:31 PM on November 17 and was cleared by the air traffic controller.

Two IndiGo plans came dangerously close to each other over Delhi's Indira Gandhi International (IGI) Airport on November 17 when the vertical and lateral separation between them went below the minimum permissible levels. The aircraft involved in the incident were Airbus A321 bearing registration VT-IUO and Airbus A320 (VT-ISO).

An IndiGo airlines passenger aircraft taxis on the tarmac.

The first plane was operating a Delhi-Hyderabad flight, while the second was flying to Raipur from Delhi. An investigation is being conducted by the Aircraft Accident Investigation Bureau (AAIB) which called it a “serious incident”.

What has the initial report revealed?

“At the time of the closest vertical separation (400 feet), lateral separation was 1.2 NM (nautical miles). At the time of the closest lateral separation (0.2 NM), vertical separation was 800 feet. There was no injury to any of the occupant on board in both aircraft. There was no damage,” the AAIB said in its preliminary report.

As per the report, the A321 departed at 12:31 PM on November 17 and was cleared by the air traffic controller. But the aircraft “was observed turning left toward the takeoff path of RWY 29R (Runway 29 Right)”. At that time, the A320 received departure clearance and took off from Runway 29 Right.

“During this sequence, a breach of separation occurred…triggering a Current Conflict alert,” the AAIB said. Both aircraft received TCAS-RAs (Traffic Alert and Collision Avoidance System-Resolution Advisory) provided by the Traffic Alert and Collision Avoidance System to pilots.

How did the AAIB obtain data?

The AAIB obtained the data from the aircraft’s cockpit voice recorders and flight data recorders, among others. The probe agency has also recorded the initial statements from the concerned flight crew and air traffic controllers, Indian Express reported.