New Delhi, Aug. 9 -- The Aircraft Accident Investigation Bureau (AAIB) is investigating an Air India flight from Phuket to Delhi on August 4 after the aircraft experienced a sudden loss of altitude of approximately 300 feet during cruise, following which the aircraft stabilised and subsequently landed safely at Delhi.

"The occurrence has been classified as a Serious Incident and is under investigation by the AAIB," the Ministry of Civil Aviation said in a statement on Sunday.

The statement added that the "both flight crew members underwent the prescribed psychoactive substance screening test. The screening test in respect of the Pilot-in-Command (PIC) indicated a result requiring confirmatory testing."

During the occurrence, injuries w...