The Directorate General of Civil Aviation (DGCA) said it has taken cognisance of the incident in which a Jet Airways flight descended 5,000 feet mid-flight between Mumbai and Brussels over Turkish airspace last week.
"DGCA has appointed a three-member team to do a training audit of Jet Airways to find out whether there are any shortcomings in their training. The team has been asked to submit its report by Aug 31," the aviation regulator said.
According to the DGCA, both the pilots including flight commander and first officer allegedly fell asleep over Turkish airspace which led to the plane descending from 34,000 feet to 29,000 feet.
An alarmed Air Traffic Control (ATC) at Ankara then contacted the Jet Airways' Boeing 777-300 aircraft asking it to resume the altitude assigned to it. This air corridor over the region has become a busy airspace with many airlines using it to avoid flying over Ukraine and Iraq.
However, the incident would have gone unnoticed if it was not for an anonymous mobile message about the uncontrolled descent to DGCA's joint director general Lalit Gupta on Tuesday, who is in-charge of air safety.
Sources in the aviation regulator said that under the set guidelines the pilots did not file the flight safety report (FSR) about the descent nor did the airline inform the DGCA.
Both the pilots have been taken off the duty roster pending inquiry and have been questioned about the incident.
Another baffling question surrounding the incident is the role of the co-pilot who said she did not realise the descent. After being questioned by the DGCA, the co-pilot said she was busy on her electronic flight bag (EFB) - a tablet that has all aircraft documents loaded on to it.
The commander of the Boeing 777 aircraft was taking a 'controlled rest', which means a nap as per rules, leaving the co-pilot as in-charge.
"Additionally, the aircraft accident investigation bureau has been asked to conduct a detailed investigation into the incident which would take four-five months," the regulator added.
DGCA will now rely on the pilots' conversations recorded in the digital flight data recorder (DFDR) and the cockpit voice recorder (CVR).
Jet Airways said it has initiated an internal inquiry into the matter, while extending all co-operation to DGCA by providing necessary assistance for the inquiry.
"Safety is of paramount importance to Jet Airways, as is also the welfare of our guests and crew and the airline will always take appropriate steps to ensure the same," the airline said in a statement.