It was found that there was no blaze or even smoke in the cabin of the 9W-2302 Mumbai-Chennai flight, which was then taxiing to the runway and was stopped on the taxiway by the pilot, Directorate General of Civil Aviation (DGCA) said.

The red flicker emanating from the anti-collision light at the bottom of the Boeing 737-800 fuselage created an optical illusion that was mistaken for a fire by the crew members, the final probe report on the August 27 incident at the Mumbai airport said.

The DGCA blamed the captain for "over-reacting" to the situation and ordering evacuation even after all indicators inside the cockpit showed there was no fire. There were 139 passengers on board.

The cabin crew was also blamed for not ensuring proper preparation for evacuation and failing to give proper instructions to the panic-stricken passengers, leading to "chaos inside the cabin".

Four passengers were seriously hurt and 21 received minor injuries as they rushed out through the over-wing exit and jumped off the slide chutes that were deployed and inflated, the 35-page report said.

"It is the illusionary situation due to the red light emanating from the anti-collision light at the bottom of the fuselage in line with the wing, which reflected on the bottom of the wing with quick intermittency," it said.

"All the crew also realised their unawareness about the effect of the anti-collision light," the DGCA report said. The Captain "completely relied on the illusionary information, failed to judge the situation" and ordered precautionary evacuation.

Noting that evacuation is ordered only in an emergency, it said in such a "non-emergency" situation, "the Captain could have returned to the bay on single engine for normal de-planing of passengers".

The pilot "made wrong decision of carrying out evacuation" without situational awareness, the report said. While the cabin crew was trained for evacuation, they were "not given training to recognise fire from the engine", nor were they taught to identify "the locations and the importance of certain navigational aids and anti-collision lights during their training", the probe report said.

The crew members also "failed to ensure orderly and injury-free evacuation", it said, adding that one of the additional crew members "made unwanted movements towards the over-wing exit" which adversely attracted the passengers "leading to the chaos in the cabin".

The aviation regulator, besides recommending action against all those involved in incident for their lapses, suggested a review of the Safety and Emergency Procedure training for the crew members by the airline.