Why Air India Phuket-Delhi flight probe won't stop at 'human' hand

A broad-based inquiry is examining the plane's systems, data and chain of events, with no conclusion yet that pilot caused the 300-ft altitude dropThe investigation into an Air India flight that suffered a sudden altitude drop during its Phuket-New Delhi journey has brought back into focus an old but difficult question in aviation safety: how much do human factors, including pilot performance and fitness, contribute to an in-flight occurrence?On August 4, an Airbus A320 (VT-EXO) operating Air India flight AI2379 from Phuket to New Delhi experienced an altitude variation of about 300 ft while cruising. The plane subsequently stabilised and landed safely in New Delhi. Twenty passengers and four cabin crew members were injured. There were 137 passengers, including three infants, and eight crew members—two pilots and six cabin staff—on board.The government’s Aircraft Accident Investigation Bureau (AAIB) has taken up the probe based on information received from the Directorate General of Civil Aviation (DGCA) and the nature of the occurrence. The ministry of civil aviation said the probe was being conducted under applicable provisions and International Civil Aviation Organization (ICAO) protocols.The probe has an international dimension. France's aviation investigation authority, the Bureau d'Enquetes et d'Analyses pour la securite de l'aviation civile (BEA) and technical representatives from Airbus are assisting AAIB with technical information and design documentation. The civil aviation ministry said such participation was part of the international investigation framework under ICAO protocols. What is significant is the breadth of the AAIB's inquiry. In addition to examining the aircraft and its systems, the bureau will review recorded flight data, operational and maintenance records and medical information, and conduct interviews with persons of interest, the ministry said.That introduces human factors into the inquiry, but there's at this point no official determination that altitude variance was due to pilot impairment or error. The entire incident has generated specific interest due to the pilot's reported psychoactive-substance test. However, a test result alone is not proof of impairment at the time of an occurrence or that it was a factor in what happened on AI2379.Captain Sam Thomas, president of the Airline Pilots Association of India, said multiple hydraulic failures can cause loss of altitude. “There was no turbulence. There were multiple hydraulic failures. The pilots took actions as per textbook—perfect actions,” he said.Civil aviation minister Kinjarapu Rammohan Naidu has said the government is treating the incident “very seriously” and that aviation safety is its highest priority. After the incident, Naidu visited injured passengers in hospital along with the civil aviation secretary and the DGCA chief. The ministry said eight passengers and four cabin crew members had been admitted for evaluation and treatment while the aircraft was sent to the hangar and its flight data recorder and cockpit voice recorder secured.Later, Naidu said the intense turbulence was said to have lasted for four to five minutes. He praised the cabin crew for their efforts to continue helping passengers who were injured.Over reports of the pilot’s marijuana test allegedly coming positive in a confirmatory lab test, the minister said there was no room for compromise on aviation safety by airlines, regulators or anyone for that matter. Should the investigation reveal that the prevailing drug use regulations were insufficient, the government would consider amending or toughening these laws, he assured.The AAIB has said that while the investigation is ongoing, it cautions “against making any conclusions based on isolated information”. Investigators are looking at the chain of events and the conditions in which they unfolded.Modern commercial aircraft have multiple layers of automation and safety systems. Yet when something unexpected happens in flight, what happens inside the cockpit is always critical. The way pilots perceive an event, divide responsibilities, communicate with each other and respond to warnings or changes in aircraft behaviour can all become relevant to an investigation.Such human factors have been investigated previously in aviation incidents. In December 2024, an Air India A320 plane, flying from Goa to Hyderabad, was taking off from a taxiway instead of the runway. The crew aborted take-off after being alerted. A “situational awareness deficit” was the likely cause, according to the AAIB probe, which also concluded that the crew didn't follow taxiing directions completely. The report also investigated things such as electronic flight bag problem and lack of an advanced surface movement guidance and control system at the airport. The incident highlighted how even a “small” lapse in situational awareness could escalate into a serious accident.In another incident, an Air India plane had overshot the runway during landing in New Delhi in June 2017. The AAIB determined that touchdown delay and low deceleration due to inadequate brake application led to the occurrence, with resultant tyre burst. It also noted that the approach had been unstable prior to landing, and investigated the crew’s management of the approach and braking.These investigations give an impression of the rationale behind the usual approach of seeking explanations beyond the actions of one crew member. Cockpit error may be brought about by several contributing factors, including workload and communications, procedures, training, environmental conditions and organisational systems.The same protocol applies to the AI2379 investigation. The AAIB has not identified a suspected cause. Instead, it has said that it will gather and preserve the relevant evidence and examine it in its entirety before drawing conclusions.There are several questions that the investigation will have to answer about the critical moments during the Phuket-New Delhi flight. The approximately 300-ft altitude variation could potentially have involved atmospheric conditions, aircraft systems, crew actions or a combination of factors. The AAIB's statement does not identify any of these as the cause at this stage.Air India's own account of the incident has also evolved. Its initial statement described the event as “brief in-flight turbulence resulting in momentary change in altitude”. A later formulation referred to a “sudden loss of altitude during cruise” and did not repeat the turbulence explanation. Reports have since raised questions about possible technical or flight-control issues. But these remain matters for the investigation to establish.Air India had initially said it knew post-flight drug testing had been conducted under the applicable protocol but had not received the results and therefore could not comment on them. After reports emerged that the pilot's sample had allegedly tested positive for marijuana, the airline did not comment on the reported finding. It has said it conducts crew drug tests under civil aviation rules and would cooperate with the authorities.Airbus, the aircraft’s manufacturer, has stated that it is cooperating with the investigating authorities concerned as per the international framework and making its experts and technical information available to Air India.Subscribe to India Today Magazine- EndsPublished By: Yashwardhan SinghPublished On: Aug 12, 2026 19:14 IST