NEW DELHI: European aerospace major Airbus and France's Bureau of Enquiry and Analysis for Civil Aviation Safety will join the probe to establish what caused the Air India A320 flying from Phuket to Delhi with 145 aboard to suddenly lose altitude by about 300ft last week, injuring many on board.Led by India's Aircraft Accident Investigation Bureau (AAIB), the investigation is examining the twin aspects of the aircraft's mechanical issues and pilot behaviour. Everyone TOI spoke to said what happened mid-flight was indeed "a close shave". Luckily, the aircraft (AI 2379) landed safely at its destination, but 17 people had to be hospitalised.The captain's psychoactive substance screening test was not negative, and the confirmatory test result is not yet officially known.

His behaviour on board is under the scanner. "One of the pilots fell in the cockpit and had to be assisted by cabin crew to get back on his seat," said a source. The flight data recorder will reveal mechanical failures, if any, and the cockpit voice recorder will reveal what transpired on the flight deck."Airbus is sending its team to India, and they will reach by Wednesday to inspect the aircraft and work with Air India and AAIB.

Being a serious incident, the investigator of the original equipment manufacturer's country (France in this case) is also coming," said a source. An Airbus official said it is "providing technical assistance to the investigating authorities. We are actively supporting the airline and will provide further information as it becomes available".Industry executives said the A320 (VT-EXO) may have suffered a triple hydraulic failure for a few seconds, which is rare.

This system uses a fluid under pressure to drive machinery or move mechanical components to power critical elements like wheel brakes, nose wheel steering, landing gear retraction/extension and flight control surfaces. It is also learnt the autopilot became disengaged during that tumultuous time for a few seconds, and the aircraft even got a stall warning.

A pilot then steadied the aircraft by pushing the nose down.AI said it can't "comment on any findings or observations related to the investigation" as it "is being conducted by AAIB" and that the airline "will continue to extend our full cooperation to authorities as required". The flight data recorder will reveal the timestamps of the sequence of events - whether the alleged transient hydraulic failure occurred because of the aircraft's rapid descent or whether the aircraft first entered an air pocket and subsequent turbulence caused hydraulic failure.