NEW DELHI — Air India pilots will undergo mandatory drug screening starting Thursday, according to an internal memo seen by AFP, after a captain involved in a serious mid-air incident reportedly tested positive for marijuana. Existing rules require airlines to randomly test at least 10 percent of their flight crew for psychoactive substances each year. "We have decided to undertake a full screening of all Group pilots for any substances or medications that are not permitted under prevailing regulations," the memo said. "Testing is mandatory and will start today." On August 4, at least 24 passengers were injured when an Airbus A320 lost about 300 feet (91 meters) of altitude shortly after departing from Thailand's Phuket for New Delhi. Local media reports said the main pilot had smoked marijuana and had tested positive in a second confirmatory test. Air India said the results have not been shared with them. Indian investigators have not commented on the reports but said they were closely examining evidence linked to the flight. The inquiry is being supported by Airbus and France's civil av