Defense News reports that five Antonov AN-32 military transport aircraft have gone missing in Ukraine. According to an Indian Air Force official, the last five out of 40 AN-32s undergoing upgrades at the Kiev-based Antonov State Company have become “untraceable.”

“These five aircraft are almost lost as it is difficult to trace them and diplomatic efforts to find their whereabouts have failed,” the Air Force official stated.

Indian Defense Minister Manohar Parrikar also said in an interview that the planes were “stuck” in Ukraine due to the ongoing fighting in the country.

In 2009, the Indian Air Force signed a contract with Ukrspetsexport Corporation, Ukraine’s state-owned arms trading company, to upgrade its 104 AN-32 transport aircraft and extend their service life for another 25 to 40 years.

The $400 million upgrades were set to include improved avionics, modernization of the cockpit, and a payload capacity increase from 6.7 to 7.5 tons, according to Defense News. It also involved a technology transfer agreement between India and Ukraine, with 64 planes domestically overhauled at the Indian Air Force’s base repair depot at Kanpur through 2017.

However, “the local upgrade at the Kanpur depot, which began three years ago, halted last year. Six aircraft were put for upgrade but work had to be discontinued as the Ukraine engineers left and only one container of spares from Ukraine had arrived,” Defense Newsreports.

According to RT, the upgrade also involved shipment of parts from Russia.

The Indian government wants to step up its strategic airlifting capacity and be able to quickly deploy forces to the Chinese and Pakistani borders and anywhere else domestically should contingencies arise.

Consequently, with the uncertainty surrounding the AN-32 upgrade program, the Indian Air Force is in critical need of increased military transport capacity according to Bhim Singh, a retired Indian Air Force wing commander.

“As AN-32 formed the bulk of the medium-lift segment of the transport fleet, urgent replacement of the Avro fleet, finalization of the joint development of medium transport aircraft and possible fresh purchases are some of the options which IAF will need to work on an urgent basis,” he said.

The Indian Air Force operates a host of different transport planes including five C-130J Super Hercules, 17 Iljushin II-76s, a number of Dornier Do 228s, and more than a dozen Boeing C-17 Globemaster IIIs.

Additionally, India is seeking to replace its aging fleet of 56 Avro transport planes. So far no contract has been awarded to defense firms bidding for the estimated $3.5 billion tender, although there are media reports that the tender had been cancelled all together in favor of a Indo-Russian joint venture.

According to TASS, India and Russia are jointly developing a new medium transport military aircraft and have co-founded a new company, the Multi Role Transport Aircraft Ltd., established by Russia’s UAC and Hindustan Aeronautics, both of which invested $300 million in the project.

The new plane is expected to enter service by 2018.  According to TASS, India plans to purchase 45 and Russia around 100 aircraft.