An Air India flight that injured passengers when it plunged midair last month suffered a temporary loss of hydraulic systems, investigators said on Friday, as the airline fired the captain who tested positive for psychoactive substances.

The Airbus A320, carrying 137 passengers and eight crew, suddenly lost altitude on August 4 while flying from Phuket, Thailand, to New Delhi, injuring 24 people before stabilising and landing safely. India’s civil aviation ministry classified it as a “serious incident”.

Both Airbus and France’s civil aviation safety agency, the BEA, said they are assisting the Indian investigation into the flight.

A preliminary report released on Friday by India’s Aircraft Accident Investigation Bureau (AAIB) said the flight-control system detected the loss of three hydraulic systems for several seconds.

“The aircraft encountered altitude upset,” it read. “Initially, it gained 372 feet and fell by 292 feet.”

The hydraulic failure caused the autopilot to disengage and triggered a two-second stall warning before the systems recovered and the aircraft returned to normal operation, the report said.

The inquiry also said the pilot in command “was found non-negative for psycho-active substance in the confirmatory test”.

“The confirmation of use of psycho-active substance is a serious concern,” the report read.

A spokesperson for Air India said the pilot has been “terminated with immediate effect”, in line with the company’s “zero-tolerance approach to violation of safety, fitness or regulatory requirements”.

Following the incident, India’s aviation ministry said the regulator was considering tighter screening rules for psychoactive substances. Air India ordered a mandatory one-time drug screening of all of its pilots last month.

The investigation is the latest challenge for Air India, owned by India’s Tata Group, which has struggled to turn around the carrier following a series of setbacks. The airline has also been hit by flight disruptions linked to the war in the Middle East.

The biggest blow to the airline’s image came in June 2025, when Air India Flight 171, a London-bound Boeing 787 Dreamliner, crashed shortly after take-off from Ahmedabad, killing all but one of the 242 people on board and 19 people on the ground.

The Indian carrier appointed Tewolde Gebremariam as its new chief executive last month, betting that the former Ethiopian Airlines chief will be able to steer Air India out of the current storm and towards profitability.