An Air India Airbus A320 flying from Phuket to Delhi suffered a sudden loss of altitude after multiple cockpit warnings indicated a possible stall, with an internal safety report revealing that the aircraft also recorded abnormal indications across its hydraulic systems.

Flight AI-2379, carrying 137 passengers and eight crew members, was operating on August 4 when the aircraft abruptly lost about 300 feet of altitude during cruise. At least 20 passengers and four crew members were injured in the incident.

The Directorate General of Civil Aviation (DGCA) has classified the episode as a serious incident, while the Aircraft Accident Investigation Bureau (AAIB) is examining what caused the aircraft to pitch sharply upward before the pilots carried out a stall-recovery manoeuvre.

Stall warning triggered

According to an internal Air India Flight Safety report accessed by NDTV, the captain was standing behind the first officer's seat and discussing the aircraft's air-conditioning system when multiple warnings appeared in the cockpit.

The aircraft's autopilot disengaged and its nose pitched upward. At the same time, aural warnings and alerts on the Electronic Centralised Aircraft Monitor (ECAM) indicated a stall condition.

The first officer, who was flying the aircraft at the time, responded with a standard stall-recovery action by pushing the nose down to regain airspeed.

The manoeuvre resulted in a sharp negative-g excursion, briefly causing the aircraft to experience conditions in which occupants and loose objects in the cockpit became effectively weightless.

Aircraft descended 300 feet

The captain's account in the report describes being thrown upward along with loose objects in the cockpit. He reportedly helped steady the first officer before moving back towards his seat.

Once strapped in, the captain took control of the aircraft and applied maximum continuous thrust to arrest the loss of airspeed and altitude.

The aircraft ultimately lost a maximum of approximately 300 feet before recovering.

An amber warning subsequently indicated that the aircraft had exceeded its negative-1g structural limit during the event.

Multiple hydraulic warnings recorded

The incident took a more serious turn when engineering data showed unusual indications from the aircraft's three hydraulic systems.

According to the report, the aircraft recorded low-pressure indications involving the Green, Blue and Yellow hydraulic systems within the same minute. The systems are designed to operate independently and provide redundancy for critical aircraft functions.

The aircraft also recorded an elevator fault and autopilot disengagement.

Investigators are examining whether a problem involving the elevator or hydraulic systems contributed to the sudden pitch-up that preceded the stall warning.

Hydraulic systems are crucial to an aircraft because pressurised hydraulic fluid powers several major functions, including flight-control surfaces, landing gear and braking systems.

Additional cockpit cautions appeared

After the aircraft stabilised, the crew notified air traffic control and began checking the various warnings.

A "door arm forward emergency" caution appeared on the ECAM and reportedly reappeared twice. The pilots followed the relevant manufacturer procedures and checklists before determining that the warnings could have been spurious.

A separate transient hydraulic caution was also recorded and cleared through the aircraft's reset procedure.

The pilots eventually decided to continue to Delhi and landed the aircraft safely.

Passengers and crew injured

Following the incident, the captain left the cockpit to assess the condition of passengers and crew members.

He was informed that several passengers and two cabin crew members had suffered serious injuries. Some cabin equipment was also damaged during the sudden aircraft movement.

The crew requested an ambulance, medical personnel and orthopaedic specialists to be available after landing. They also requested a parking position closer to the runway exit to facilitate the evacuation of injured passengers.

The aircraft eventually landed safely in Delhi.

AAIB, DGCA investigating incident

The AAIB has begun a detailed investigation into the incident under the framework of Annex 13 of the International Civil Aviation Organisation.

Airbus and France's Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) are providing technical assistance.

The Ministry of Civil Aviation said investigators are examining technical, operational, medical and human-factor evidence. This includes aircraft systems, recorded flight data, maintenance records, medical information and interviews with people connected to the incident.

The ministry has stressed that no final conclusion should be drawn until all available evidence has been examined.

Pilot drug-test reports emerge

The investigation has also drawn attention to the pilots' mandatory post-flight psychoactive substance screening.

According to sources cited in media reports, the first officer tested negative, while the captain reportedly failed two tests for marijuana.

Both pilots have reportedly been removed from flight duty pending further investigation.

The reported test results are separate from the technical investigation into the aircraft's sudden pitch-up, hydraulic indications and loss of altitude. Investigators are expected to examine all relevant operational and human factors before determining the cause of the incident.

Air India and ministry under scrutiny

Air India's outgoing CEO Campbell Wilson met senior Ministry of Civil Aviation officials following the incident.

Civil Aviation Minister Ram Mohan Naidu said aviation safety remains the ministry's highest priority and that the incident was being taken seriously.

The investigation will now focus on whether the aircraft's hydraulic and elevator indications were connected to the sudden pitch change, why the stall warning was triggered and whether any additional technical or human factors contributed to the event.

Until the AAIB completes its investigation, the precise cause of the 300-foot descent remains under examination.