What was found
MTY - FLIGHT 4921, THE CREW REPORTED SMOKE IN THE COCKPIT WHEN THE NR 1 PACK WAS SELECTED ON. MX PLACED THE NR 1 PACK ON MEL, AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE. THE ACFT LANDED IN IAH WITHOUT INCIDENT. MX INSPECTED THE ACFT, R&R THE NR 1 ENGINE, OPS TESTED WITH NO DEFECTS, REMOVED THE MEL, AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.