New Delhi:The Aircraft Accident Investigation Bureau (AAIB) will probe the Air India Phuket-Delhi flight altitude loss, as the Civil Aviation Ministry, on Sunday, termed the incident a serious one. The two flight crew members underwent the psychoactive substance screening test, following which the pilot needed to undergo a confirmatory test. "As part of the Standard Operating Procedures following such an occurrence, both flight crew members underwent the prescribed psychoactive substance screening test. "Pending investigation and completion of the prescribed process, both flight crew members have been taken off roster by the DGCA. The Air India flight departed Phuket at 8:25 am and landed safely in Delhi at 11:50 am (Indian Standard Time).