A leaked internal email from a private airline has blamed the freak accident, which caused the death of an Air India (AI) engineer after he got sucked into of the plane at the Mumbai international airport, on lapse in protocol, reports said.

The bizarre accident occurred as the Mumbai-Hyderabad flight AI 619 began its pushback at 8:46 pm on Wednesday. According to Indian Express, both Air India and the Directorate General of Civil Aviation (DGCA) have ordered for an enquiry.

The deceased has been identified as Ravi Subramaniam, a 56-year-old Vashi resident, who worked as a service engineer. His responsibilities included disconnecting the pushcart from an aircraft before it moves towards the runway.

The leaked letter, written after interviewing the staff at the Chatrapati Shivaji Airport, suggests Standard Operating Procedure (SOP) were not followed as the AI Mumbai-Hyderabad flight prepared for take-off.

A helper was with the victim and had a narrow escape as he ducked when the aircraft began moving.

"The helper removed the tow bar and in all this time, the technician (Subramaniam) was facing the tow truck with his back towards the engine. In the meanwhile as per information, captain got taxi clearance from ATC (Air Traffic Control) and he was informed by co-pilot the [area around the] aircraft is clear, (sic)" the email read, according to Hindustan Times.

An NDTV report said the internal email was written by Pradeep Singh Rawat, a maintenance manager for IndiGo in Mumbai. Rawat, in his email, suggested there was a clear lack of coordination between the ground staff and the  ATC.