An Air India flight travelling from Phuket to Delhi faced a serious technical emergency on August 4 when all three of its hydraulic systems stopped functioning for a short period at an altitude of around 36,000 feet. The incident affected the aircraft's flight controls and caused a sudden change in altitude, leaving several passengers and crew members injured. The aircraft involved was an Airbus A320 operating as AI2379. There were 145 people on board, and 24 people suffered injuries during the incident, including four who were seriously hurt. The aircraft later regained normal control and continued its journey to Delhi, where it landed safely. The incident has attracted attention because an Airbus A320 is designed with three separate hydraulic systems to provide additional protection if one system fails. The systems are known as green, blue and yellow. Normally, the loss of one system should not cause a complete loss of hydraulic control.

What Happened at 36,000 Feet?

The aircraft was flying normally when the flight-control system detected a problem with its hydraulic pressure. The first failure involved the green system. About four seconds later, the other two systems were also detected as unavailable. The autopilot then disconnected. During the brief loss of hydraulic support, the aircraft first climbed above its assigned altitude before descending. Passengers who were not wearing seat belts were lifted from their seats and struck the aircraft's ceiling and interior fittings. The event caused damage inside the cabin, including cracked ceiling panels, displaced overhead-bin doors and damaged fittings.

Why the Hydraulic Failure Is So Unusual

The Air India hydraulic failure is unusual because the three systems are intentionally separated. Each system has its own reservoir and different sources of pressure. Their design is meant to prevent one technical problem from disabling all three at the same time. The aircraft uses hydraulic power for several important functions, including flight-control surfaces, landing gear, brakes and wing flaps. Losing hydraulic pressure can therefore create major operational difficulties. Previous aviation incidents have shown that separate hydraulic systems can sometimes be affected by one physical event. However, investigators have not identified such an event in the Phuket-Delhi case so far.

Investigators Still Searching for the Cause

The AAIB investigation is examining whether the aircraft genuinely lost hydraulic pressure or whether some of the sensors or related electrical systems incorrectly reported a loss. Airbus has also examined the aircraft and requested checks of hydraulic pressure sensors, switches and wiring. Structural inspections were also sought because the aircraft experienced forces outside specified limits during the incident. The Air India A320 later recovered normal hydraulic pressure, allowing the flight crew to regain control and continue safely to Delhi. Investigators are also examining maintenance records and components removed from the aircraft. The aircraft had earlier been operating under a minimum-equipment provision involving an inoperative power transfer unit, although the investigation has not established a connection between that issue and the August 4 event.

Pilot Drug-Test Issue Adds Another Safety Question

The Air India flight incident has also drawn attention because the pilot-in-command returned a non-negative result for a psychoactive substance during post-flight testing. However, the preliminary investigation has not established that the test result caused or contributed to the hydraulic malfunction. Air India has since taken additional safety measures, including broader testing of its pilots, while regulators have been urged to strengthen action against substance abuse in aviation.

What Is Still Unknown?

The central question in the Phuket Delhi flight incident remains why three independent hydraulic systems appeared to fail almost together and then recovered within seconds. Investigators must determine whether the systems actually lost pressure, whether a common technical issue affected their readings, or whether another problem caused the flight-control disruption. The final investigation is expected to provide a clearer explanation. Until then, the incident remains an unusual case involving a temporary loss of all three hydraulic systems on a modern passenger aircraft.

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What happened to the Air India Phuket-Delhi flight?

The aircraft temporarily lost all three hydraulic systems while cruising at about 36,000 feet, causing an altitude upset and injuries to 24 people.

How many hydraulic systems does an Airbus A320 have?

An Airbus A320 has three independent hydraulic systems: green, blue and yellow.

Did the Air India aircraft land safely?

Yes. The hydraulic systems recovered and the aircraft continued to Delhi, where it landed safely.

What caused the hydraulic failure?

The exact cause has not yet been established. Investigators are examining hydraulic components, sensors, switches, wiring and maintenance records.

Air India Phuket-Delhi Incident

The incident involved Air India flight AI2379 travelling from Phuket, Thailand, to Delhi, India. The aircraft experienced the hydraulic-system failure while flying over India during its journey to Delhi. The investigation is being handled by India's Aircraft Accident Investigation Bureau, with technical support from Airbus and other aviation authorities.