New Delhi, Aug. 17 -- Air India's sweeping screening of its pilots has returned "non-negative" initial results for psychoactive substances in two of around 300 pilots tested so far, a person familiar with the matter said. The results, which still require confirmation, come as the Tata-backed airline steps up checks on its cockpit crew following the recent Phuket-Delhi incident.

The airline began mandatory testing of its entire pilot workforce on 13 August.

A "non-negative" result does not by itself establish that a pilot has consumed a prohibited substance. This requires a second set of confirmatory tests.

The development comes days after the pilot-in-command of the Air India Phuket-Delhi flight returned positive for a banned substance...