2016's biggest mystery: Missing IAF AN-32

The Indian Air Force's AN-32 plane, which was en route to Port Blair from Chennai, went missing over the Bay of Bengal on July 22. The disappearance of the Russian-made Antonov An-32 twin engine turboprop transport aircraft kicked off India's biggest search operation yet for a missing plane on the sea.

Twenty-nine people were on board the plane when the incident occurred.

Despite a number of efforts, the officials of the Navy, Indian Air Force, and Coast Guard could not locate the missing plane. And in September, the 29 people on board the AN-32 plane were declared "presumed dead".

However, officials from both the IAF and Navy said the search for debris of the ill-fated aircraft would continue.

The aircraft, an upgraded AN-32 belonging to 33 Squadron, took off from Tambaram Air Force Station in Chennai at 8.30 am, and was expected to land at Port Blair in the Andaman and Nicobar Islands at 11.30 am, in what officials said was a "routine sortie". However, the plane never landed.

As per the recorded transcript of air traffic radar, the last signal from the aircraft was 151 nautical miles east of Chennai when it took a left turn with rapid loss of height from 23,000 feet.

Indian Navy and Coast Guard ships were deployed for scanning the surface of the sea as part of the search operations after the aircraft went off radar.

Also, data from Indian satellites were scanned to locate the missing aircraft.

Reports suggested that the aircraft was not fitted with an underwater locator beacon, which made the search operations even more difficult.

The plane had on board six crew members, 15 personnel from the IAF, Army, Navy and Coast Guard, and eight civilians who were family members of the personnel.

According to Aviation Safety Network data, an online portal that tracks airliner accidents across the world, as many as 15 AN-32 aircraft of the IAF crashed between 1986 and 2014.

The AN-32 plane is a medium tactical transport aircraft that can carry 39 troops and five crew.