India's civil aviation regulator has ordered Jet Airways to suspend two pilots after a flight to Brussels dived 1,500 metres, forcing air traffic controllers to issue an emergency warning.

The Times of India said the captain was on a scheduled rest break when the plane dropped over Turkey, putting it at an altitude assigned to another aircraft last Friday.

Air traffic controllers in Ankara had to issue an emergency warning to the co-pilot on duty, who the paper said "did not notice that the aircraft had lost altitude" because she was using her tablet computer at the time.

The Director General of Civil Aviation (DGCA) on Thursday said it had summoned the captain and co-pilot for questioning over what it called a "serious incident" during the flight from Mumbai to Brussels while it was reportedly carrying 280 passengers.

"Both the pilots have been taken off the roster pending inquiry," said the regulator in a statement.

"Additionally, the Aircraft Accident Investigation Bureau has been asked to conduct a detailed investigation into the incident."

The airline said it had launched its own investigation.

"Safety is of paramount importance to Jet Airways, as is also the welfare of our guests and crew," it said in a statement.

Safety rating

Jet Airways, in which Abu Dhabi-based Etihad Airways has a 24 percent stake, is India's second-biggest carrier.

India's air passenger market has expanded at breakneck speed, but many companies are laden with debt due to fare wars, high fuel costs and shoddy infrastructure.

In 2011, the airline sector was shaken by a scandal over a number of unqualified Indian pilots flying on fake licences.

In January the US Federal Aviation Administration (FAA) stripped the country of its top safety rating, citing a lack of safety oversight.

It downgraded India's aviation safety rating to category two from category one, putting it in the company of such countries as Zimbabwe, Bangladesh and Indonesia.