A preliminary investigation into the August 4 Air India Phuket-Delhi flight incident has found a sequential failure of all three hydraulic systems of the Airbus A320neo, while the pilot-in-command (PIC) was also found non-negative for a psychoactive substance in post-flight testing.
The Aircraft Accident Investigation Bureau (AAIB) has recommended that the Directorate General of Civil Aviation (DGCA) take appropriate action regarding the toxicology finding. The investigation into the technical failure, the aircraft’s sudden altitude change and the circumstances surrounding the incident is continuing, and the preliminary findings do not establish that the pilot’s test result caused the aircraft’s loss of altitude.
Flight Lost Around 300 Feet of Altitude
Air India flight AI 2379 was operating from Phuket to New Delhi on August 4 with 145 people on board, including 137 passengers and eight crew members.
During cruise over Odisha, the aircraft experienced a rapid sequence of failures involving its primary hydraulic systems. The Green system failed first, followed shortly by the Blue and Yellow systems. The hydraulic pressure subsequently returned, allowing the pilots to regain normal control of the aircraft.
The aircraft briefly climbed before descending by roughly 292 feet from its cruising level. The sudden change in altitude caused people inside the cabin to be thrown around, resulting in multiple injuries.
Three Hydraulic Systems Failed
The Airbus A320neo uses three hydraulic systems to operate important flight-control functions. The preliminary findings indicate that the three systems lost pressure in quick succession during the incident.
The failure also caused the autopilot to disengage and triggered cockpit warnings, creating a critical situation for the flight crew. Earlier technical assessments had similarly pointed to a rare triple-hydraulic failure as the key mechanical issue behind the sudden altitude change.
The aircraft had also been operating under a Minimum Equipment List provision because of an inoperative Power Transfer Unit (PTU), according to the preliminary report details reported on Friday. Investigators are examining the relationship, if any, between the aircraft's existing technical condition and the subsequent hydraulic failures.
Pilot's Psychoactive Substance Test Raises Concern
The preliminary report has separately highlighted the toxicology findings involving the pilot-in-command.
Because the flight originated outside India, both pilots underwent mandatory post-flight medical screening. Both reportedly cleared the alcohol breathalyser test. However, the PIC's initial screening for psychoactive substances returned a non-negative result, while the co-pilot's test was negative. A subsequent confirmatory laboratory test also found the PIC to be non-negative for a psychoactive substance.
AAIB described the confirmation as a serious safety concern and recommended appropriate action by DGCA on priority.
Reports published earlier in August had also said that a confirmatory test had detected marijuana in the pilot's sample. However, the investigation has not established that the substance finding was responsible for the aircraft's technical malfunction or altitude loss.
24 People Needed Medical Attention
The sudden aircraft movement occurred while the seat-belt signs were switched off. According to the preliminary findings, 24 people — 20 passengers and four cabin crew members — required medical attention after the incident.
Twenty people were treated and discharged for minor injuries, while four were hospitalised with more serious injuries.
The aircraft continued its journey to Delhi after the hydraulic pressure was restored and landed safely. The incident therefore resulted in injuries inside the cabin but no crash or loss of the aircraft.
Turbulence Account Under Scrutiny
The incident was initially described as involving turbulence. Air India's first statement referred to brief in-flight turbulence and a momentary change in altitude, while a later statement described it as a sudden loss of altitude during cruise.
The subsequent identification of the triple-hydraulic-system failure shifted attention towards the aircraft's technical systems. The Directorate General of Civil Aviation had earlier described the incident as involving a suspected transient technical fault.
Investigators are continuing to examine flight-data and cockpit information to establish exactly how the hydraulic failures occurred and how the aircraft responded during those critical seconds.
Final Report Will Establish Cause
AAIB's current findings are preliminary and should not be treated as the final explanation for the incident.
The investigation is examining both the aircraft's technical failures and the circumstances surrounding the flight crew. A key question is whether any human-factor issue contributed to the event, while the technical investigation seeks to determine why all three hydraulic systems lost pressure in such rapid succession.
The final report is expected to provide a more complete assessment of the sequence of events and any safety recommendations arising from the incident.
