AI Phuket flight prelim probe confirms hydraulic failure, pilot positive for drugs

An AAIB preliminary report says Air India flight AI 2379 suffered simultaneous failure of all three hydraulic systems, causing an altitude upset and nearly 300-foot descent. The captain tested non-negative for a psychoactive substance, while the investigation continues.The preliminary report also contains a significant finding concerning the pilot-in-command. Both flight crew members underwent psychoactive substance detection tests. (File Photo: ITG)The Aircraft Accident Investigation Bureau (AAIB) has found that an Air India Phuket-Delhi flight suffered a temporary loss of pressure in all three hydraulic systems during the flight on August 4, 2026.The preliminary report also flagged a non-negative psychoactive-substance test for the pilot-in-command. The AAIB has recommended that the Directorate General of Civil Aviation (DGCA) take appropriate action on the matter.The aircraft, operating as flight AI 2379 with 137 passengers, was cruising at Flight Level 360 when the incident occurred. The aircraft’s flight-control system first detected a loss of pressure in the green hydraulic system. Within seconds, the blue and yellow hydraulic systems also showed a loss of pressure.The autopilot disengaged and a continuous repetitive chime sounded. A stall warning was subsequently triggered for two seconds. The aircraft experienced a significant altitude upset during the incident. It initially climbed 372 feet before descending 292 feet from its assigned FL360. The hydraulic systems subsequently recovered, allowing the aircraft’s flight-control surfaces to function normally.The co-pilot, who was the pilot flying at the time, initially responded to the situation before the pilot-in-command (PIC) took over the controls. The incident also resulted in injuries inside the cabin. With the seat-belt signs off, passengers and cabin crew were thrown around during the altitude upset.A total of 24 people — 20 passengers and four cabin crew members — received medical treatment after the aircraft landed in Delhi. Twenty people were discharged after treatment for minor injuries, while four people with serious injuries were hospitalised.The aircraft also sustained damage to several cabin components, including overhead ceiling panels, passenger-service units and overhead-bin doors.An emergency-exit handle and handrails were broken, while a lavatory fixture was uprooted and parts of crew seats were damaged.FLIGHT CONTINUED TO DELHIDespite the incident, the flight crew decided against diverting to the nearest en-route airport and continued towards its scheduled destination, Delhi.The crew later contacted Delhi Air Traffic Control and requested medical priority. The aircraft landed safely on Runway 11L at Indira Gandhi International Airport at 11 AM IST and taxied to its parking bay under its own power, arriving at 11:07 AM IST.The AAIB report noted that no adverse weather conditions were reported at the time of the incident, although forecasts had indicated the possibility of thunderstorms later.The aircraft had also been operating under an existing Minimum Equipment List (MEL) item, 29-23-01A, relating to its Power Transfer Unit (PTU). The MEL item had been invoked on July 28, 2026. No new discrepancy had been recorded before the aircraft departed Phuket.CAPTAIN'S PSYCHOACTIVE-SUBSTANCE TEST NON-NEGATIVEOne of the most significant findings in the preliminary report concerns the pilot-in-command's psychoactive-substance test.Both flight crew members underwent breathalyser testing and tested negative. They were subsequently subjected to psychoactive-substance screening. The PIC's sample was found to be non-negative, while the co-pilot tested negative.Blood samples from both pilots were then sent to a pathological laboratory for confirmatory testing. The PIC's confirmatory blood test was also found to be non-negative, while the co-pilot's sample remained negative.The AAIB described the confirmed finding concerning the PIC as a “serious concern” and recommended that the Directorate General of Civil Aviation (DGCA) take appropriate action on priority to address the abuse of psychoactive substances.However, the preliminary report does not establish that the captain's psychoactive-substance test had any role in the hydraulic failure or the aircraft's altitude upset.INVESTIGATION INTO ROOT CAUSE CONTINUESThe AAIB has recovered the aircraft's cockpit voice recorder and digital flight data recorder, with the recorded data downloaded for further analysis.Investigators also collected hydraulic components and hydraulic fluid samples for testing. Technical experts assigned by France's Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) and Airbus inspected the aircraft between August 13 and 15.The investigation team has also collected maintenance and operational records, fuel and oil samples and relevant information from air traffic control authorities. Initial interviews have been conducted with the flight crew, cabin crew, airline, airport operator and medical personnel.The AAIB said detailed investigation into the technical and other aspects of the incident is still underway.The preliminary report therefore does not establish the probable cause or contributory factors behind the triple hydraulic failure. The findings remain subject to further investigation, with the final report expected to determine the cause of the incident and any contributing factors.- EndsPublished By: Devika BhattacharyaPublished On: Sep 4, 2026 11:22 IST