The first C-17 heavy-lift aircraft built for the Indian Air Force arrives at Edwards Jan. 22. The 418th Flight Test Squadron will begin aircraft inspection and routine flight testing for the next two months. (U.S. Air Force by Jet Fabara)

Chennai/New Delhi: An AN-32 transport aircraft of the Indian Air Force (IAF) with 29 people on board went missing on Friday over the Bay of Bengal off the Chennai coast, and remained untraceable till evening despite a full-scale search and rescue mission.

Those on board included six crew members, 15 personnel from the IAF, army, navy and Coast Guard, and eight civilians who were family members of the personnel.

Eight of the passengers were employees of Naval Armament Depot (NAD) in Visakkhapatnam. Their families were worried over the fate of their loved ones and were anxiously waiting for some information from the ongoing search operations.

The aircraft, an upgraded AN-32 belonging to 33 Squadron, took off from Tambaram Air Force Station in Chennai at 8.30 a.m., and was expected to land at Port Blair in the Andaman and Nicobar Islands at 11.30 a.m., officials said, describing it as a “routine sortie”.

According to a report submitted to Defence Minister Manohar Parrikar by Air Force Chief Air Chief Marshal Arup Raha, according to the recorded transcript of Chennai air traffic radar, last pickup was 151 nautical miles east of Chennai, when the aircraft was observed to have carried out a left turn with rapid loss of height from 23,000 feet.

A massive search and rescue operation involving aircraft, helicopters, ships and a submarine was launched immediately to find the plane that went missing around 300 km off Chennai, and will continue through the night.

The last contact with the aircraft was established roughly around 15-20 minutes after the take-off, sources said.

As the aircraft went missing, a full-scale search and rescue operation was launched immediately.

“Efforts on to trace IAF AN 32 aircraft and our Service personnel on board,” Parrikar said in a tweet.

The Eastern Naval Command (ENC) deployed two P8I long-range maritime surveillance aircraft with advanced electro-optics and radars, two Dornier aircraft and 12 ships with integral helicopters to join the search operations.

Four ships of the ENC, deployed in the Bay of Bengal on different missions, were diverted to the search area while eight ships of the Eastern Fleet, which were on return journey from the South China Sea, were also made to proceed to join in the operations.

A submarine at sea was diverted as well for locating transmissions from the emergency locator beacon onboard the aircraft. Emergency locator beacons usually get activated in case a plane crashes.

Ships deployed for the search include Shivalik-class stealth frigate INS Sahyadri, guided-missile destroyers INS Rajput and Ranvijay, corvettes Kamorta, Kirch, Karmuk, Kora, Kuthar, fleet tankers INS Shakti and INS Jyoti, amphibious warfare vessel INS Gharial and patrol vessel INS Sukanya, the Indian Navy said. Four Coast Guard ships are also involved in the operations.

The incident comes a year after a Coast Guard Dornier aircraft with three crew members on board for a routine surveillance flight went missing.

The search team found its black box nearly a month later. The skeletal remains and personal belongings of the crew members were recovered from the sea bed off the Tamil Nadu coast.

India bought 125 AN-32 aircraft in 1984. The IAF at present has a fleet of over 100 AN-32s.

The Russian-origin aircraft is known for its excellent take-off characteristics in hot and high conditions, and is suitable for use as a medium tactical military transport. The twin-engine aircraft is primarily used for transporting cargo and passengers, including skydivers and paratroopers.

After India decided in 2009 to get the aircraft upgraded, 40 were upgraded in Ukraine and the rest in the country.

The final batch of upgraded AN-32RE aircraft was delivered last year, and the modifications have increased the life of these aircraft by 15 years to serve till 2035, according to experts. However, the modernisation programme in India was hit by the situation in Ukraine and shortage of spare parts.