Turkey is again contemplating buying Russian fighter jets.

Turkish sources told the pro-government Daily Sabah newspaper last week that Ankara was close to reaching a deal with Moscow to purchase some 36 Sukhoi Su-35s from Russia. Russian media also reported in late September that both countries were holding talks over the purchase of Su-35s, but said it was too early to talk about reaching a concrete deal.

Since his August visit to Russia, Turkish President Recep Tayyip Erdoğan has flirted with buying Russian Su-57s or Su-35s following Ankara’s removal from the F-35 Joint Strike Fighter programme by the United States over its purchase of Russian S-400 air defence missiles.

However, from the get-go, it seemed unlikely Turkey could buy and field the more modern stealthy fifth-generation Su-57 anytime soon. As military aviation expert Tom Cooper outlined, the mass production of Su-57s will unlikely commence for up to another decade.

Therefore, the only fifth-generation jet Turkey might be able to acquire in the foreseeable future – unless it can somehow get readmitted into the F-35 programme – is the indigenous fifth-generation TAI TF-X fighter it is building. But it will likely take another couple of years before there is even a flyable TF-X prototype.

In the meantime, the Su-35 might serve a significant role in the Turkish Air Force until it either acquires or builds its own fifth-generation fighter. The Su-35 is a 4.5-generation aircraft, which puts it in roughly the same league as the Dassault Rafale or the Eurofighter Typhoon.

“Turkey needs a stop-gap fighter before it brings the TF-X online, assuming that programme moves forward,” said Aaron Stein, director of the Middle East Programme at the Foreign Policy Research Institute.

“The Su-35 is basically the only Russian aircraft on the market that would fit this need for Turkey,” he said.

Levent Özgül, a Turkish defence analyst said that if Turkey bought 54 Su-35s, which would amount to approximately three squadrons, “its flyaway cost would be at least $3 billion, and that’s without any spare parts, support, training, or weapons.”

He suggested that Russia might give Turkey a new loan that could cover up to about 50-60 percent of the aircraft’s cost.

Stein does not believe that comparing platforms is a useful exercise, and said that any such deal wherein Turkey buys a fleet of Su-35s would have tremendous political repercussions.

Joseph Trevithick, a defence analyst and author for The War Zone, said that comparing the F-35 or Su-35 with Turkey’s existing fleet of F-16s is the wrong question.

“Turkey was not acquiring the F-35 to replace its F-16s, it was acquiring them to replace the F-4s,” Trevithick said, referring the Phantom jets that Turkey first began operating in 1974.

“The Phantom II is an iconic aircraft and has served Turkey well, but the Su-35 would offer a significant boost in capability over those jets, which have proven to be increasingly vulnerable in recent years,” he said, pointing to Syria’s shooting down of a Turkish RF-4E reconnaissance jet in 2012.

One issue with buying Su-35s is the compatibility of munitions. Turkey’s fleet of fighter jets consists entirely of American-built F-16s and F-4s that use American and NATO-standard weapons. Ankara would have problems using these weapons on Russian aircraft and might, therefore, have to buy them from Moscow.

“I guess in regards to the compatibility of technologies Russia would like to see a NATO member purchase Russian arms despite possible issues,” said Timur Akhmetov, an Ankara-based researcher for the Russian International Affairs Council.

“The thing is to enter the market heavily dominated by NATO/U.S. weapons systems, I would expect Russia agreeing on some joint production or even some changes in the design so as to smoothen Turkey's acquisition in terms of compatibility with Turkish-made missiles and hardware,” Akhmetov said.

At the same time, he said, some in Russia argue “that the Kremlin should be extremely cautious in its dealings and arms sales to Turkey, since it’s still a NATO-member, unless there is some certainty or political guarantees that Russian technologies wouldn’t be given to Western states.”

Stein said Turkey would likely to try to use some of its domestic munitions on the Su-35s.

“We are going to have to wait and see,” he said. “But, there can be no doubt that Russia will be critical for providing Turkey with spare parts and supplies to keep the airplane flying.”

Trevithick pointed out that while Russia jets “are not entirely incompatible with Western munitions” integrating them “does require acquiescence from those third party suppliers and any other relevant export approvals.”

“Turkey also has interoperability obligations under NATO,” he said, pointing out that it may find it “increasingly more complicated to get the necessary approvals to do this in its case than say Malaysia.”

In June 2017, Malaysia successfully dropped a U.S.-made laser-guided bomb from one of its Russian made Su-30 jets.

“At the same time, with what we’ve seen from the Trump administration or Congress lately, this may not be as complicated as feared, either,” Trevithick said.

“This sort of dichotomy, particularly in Congress, speaks to what we might see in terms of retaliation in the event of a Turkish Su-35 buy from the United States,” he said.

He recalled that the Countering America’s Adversaries Through Sanctions Act (CAATSA) was supposed to automatically slap sanctions on Turkey for its S-400 deal, but these sanctions “still haven't been implemented and it doesn't look like that will be happening any time soon”.

Özgül foresees a logistical nightmare for Turkish Su-35s given compatibility problems and predicts Turkey would also have to invest massively to keep them operational.

“The transformation of bases, bunkers, maintenance centres will need huge investments,” he said.

Özgül said the Su-35 was a highly formidable fighter with sophisticated avionics, but he also noted it had no stealth features or internal bomb bays, required a lot of maintenance and also consumed an enormous amount of fuel.

Daily Sabah said Turkey was discussing becoming involved in the production of some components, including precision weapons and ammunition.

“Moscow has made clear to its own press that it is willing to license the production of non-essential parts, so I do not think this is a major problem, so long as Turkey continues its recent trend of accepting less from Russia than what it demands from the West in defence procurement,” Stein said.

Trevithick said it was unclear how extensive Russia's offers of cooperation really were.

“But we do know that they have made similar pledges with regard to the S-400 and that Erdoğan has said that Turkey could be involved in producing components for the S-500, as well,” he said.

The real issue for Turkey was replacing the extremely lucrative contracts for the F-35 programme, Trevithick said.

Turkish firms were contracted to manufacture just under 1,000 parts for the F-35 jets and are set to lose an estimated $9 billion from Turkey’s removal from the programme.

“I think any interest in actually producing, or even just assembling, complete systems in Turkey is of secondary importance to stabilising this industrial base,” Trevithick said.