Serious incident to the Airbus A320 registered VT-TNE and operated by Vistara and to the Airbus A319 registered VT-SCA and operated by Air India on 07/02/2018 near Mumbai [Investigation led by AIB / India]

Preliminary data based on the notification from the Indian authorities:

Air India AIC631 operating from Mumbai to Bhopal and M/s TATA Singapore Airlines VTI997 from Delhi to Pune met with serious incident wherein the closest separation reduced to less than 02 NM and vertical separation was zero. It was reported by ATC Mumbai that VTI997 was given descend to flight level 290 but it descended on its own to FL 270 and subsequently was observed to pass through the level of Air India AIC631 which was cleared to FL270.Both the aircrafts reported getting RA.