Air India A320 Issued Stall Warning As Hydraulics Failed, Injuring 24: AAIB Report

A routine cruise turned chaotic aboard an Air India flight from Phuket to Delhi last month, when the aircraft briefly lost all three of its hydraulic systems and set off a stall warning even though seatbelt signs were switched off. The sudden jolt threw passengers and crew against overhead bins, leaving 24 people injured.

The Aircraft Accident Investigation Bureau released its preliminary findings on Friday, September 4, revealing that the Airbus A320, cruising at 36,000 feet on August 4, first climbed 372 feet before dropping 292 feet below its assigned altitude. Investigators traced the disruption to a rapid failure of all three hydraulic systems within a span of four seconds, an event that knocked out the autopilot and set off a continuous alarm in the cockpit.

A two-second stall warning followed shortly after. The systems began coming back online about nine seconds after the first one failed, though the report stopped short of explaining what caused the pressure loss in the first place, flagging it as a matter for further probe.

Given the extent of the disruption, investigators reclassified the event from a serious incident to a full-fledged accident. The flight was carrying 137 passengers and eight crew members. According to the report, the 32-year-old first officer had control of the aircraft when the systems failed, before the 34-year-old captain stepped in to take over. Both pilots have since been questioned by investigators.

Captain's Drug Test Raises Fresh Questions

Separately, the report noted that the captain's confirmatory test for psychoactive substances came back non-negative. Investigators did not disclose which substance was involved, though a Reuters report last month identified it as marijuana. Calling the result a serious concern, the AAIB urged the aviation regulator to act on priority to curb substance misuse among pilots.

In response, Air India said it was fully cooperating with the investigation, providing access to its operational, maintenance and technical records. The carrier has also rolled out a one-time mandatory drug test for its entire pilot workforce, going beyond what regulators currently require. Authorities are now weighing whether to make annual testing compulsory for all pilots, a sharp jump from the existing norm of testing just 10% of pilots each year.

While the AAIB's report carried no recommendations for Airbus, a separate internal analysis by the manufacturer, reviewed by Reuters, found that the aircraft's three hydraulic systems failed in close succession, briefly cutting off pilot access to critical controls. For roughly four seconds, the crew could not operate the elevators and ailerons, the components that manage the aircraft's pitch and banking motion.

The episode adds to the pressure already surrounding Air India, which has faced heightened scrutiny since a Boeing 787 operated by the airline crashed in Ahmedabad in June 2025, killing 260 people. The Tata Group controls Air India, while Singapore Airlines holds close to a 25% stake in the carrier.