Air India is to test all of its pilots for banned substances, starting immediately.
It comes after an incident last week in which its Phuket to Delhi flight suddenly lost altitude, with a preliminary report saying the senior pilot had to retake their substance test. Reports say they had tested positive for marijuana.
Pilots at the airline's budget arm, Air India Express, will also be subject to the tests from Thursday.
Existing rules require at least 10% of pilots to be tested at random.
Seventeen passengers and crew were injured when the Airbus lost about 91 metres (300 feet) in height shortly after departure on 4 August.
It is being investigated by Indian authorities working alongside Airbus and France's air safety agency.
Both pilots of the flight have been removed from duties until the investigation is complete.
In a memo seen by the BBC, Air India said it was "important to go further" in its testing.
"This initiative, which goes beyond regulatory requirements, reflects our determination to uphold the highest standards of safety and professionalism, and to provide reassurance to our passengers, stakeholders and the community at large," it said.
The airline has already been under scrutiny after a June 2025 flight from Ahmedabad to London crashed shortly after take-off, killing 241 people on board and 19 on the ground. Only one passenger survived.
The tests - for substances as well as medications prohibited under aviation regulations - are being carried out alongside training sessions at Air India's academy, as well as other locations including briefing centres and offices.
Last week, former Ethiopian Airlines boss Tewolde Gebremariam became Air India's new chief executive.
