Air India has ordered mandatory drug testing of all pilots across the group, including Air India and Air India Express, as scrutiny intensifies over the Phuket-Delhi flight incident in which the pilot-in-command tested positive for drugs.The fresh testing began on Thursday and will cover all group pilots, with the airline saying the move goes beyond existing regulatory requirements and is aimed at reinforcing safety and passenger confidence.In a communication to pilots, Air India said the screening would cover substances and medications not permitted under prevailing regulations. The tests will be conducted alongside training at the airline’s Gurugram academy, after flights at its briefing centres and offices or at locations designated by individual bases.The airline said it already complied with the testing requirements prescribed by the Directorate General of Civil Aviation (DGCA), which it said were broadly comparable with practices in other major aviation jurisdictions.The decision comes days after the pilot-in-command of Air India flight AI2379, operating from Phuket to Delhi, tested positive for drugs following the August 4 incident in which the aircraft suffered a sudden loss of altitude.The Airbus A320neo, registered VT-EXO, was carrying 137 passengers and eight crew members when it experienced the altitude variation over Odisha before landing safely in Delhi. The incident left 24 people injured, including 20 passengers and four crew members.The development has also widened scrutiny around the conduct of the flight crew and the technical condition of the aircraft. A post-flight maintenance report has recorded multiple warnings involving low hydraulic pressure, a flight-control fault affecting the elevators, autopilot disengagement and other technical messages.Meanwhile, the preliminary report into the AI2379 incident is expected to be completed within the next 10 to 15 days, sources said.The Aircraft Accident Investigation Bureau (AAIB), which is probing the incident, has summoned the pilots and cabin crew for questioning as part of its investigation.Once the preliminary findings are available, the DGCA will examine the report and decide on regulatory action against the airline, sources said.Fines and management liability cannot be ruled out at this stage, the sources said, while stressing that any such action would depend on the findings of the investigation.The airline could also face enhanced regulatory surveillance, depending on what the investigation establishes, they said.The AAIB probe is examining the incident from both technical and human-factors angles. Investigators are expected to assess flight-data recordings, maintenance records, crew statements and other evidence before determining what led to the sudden altitude loss.