Now it is unlikely the United States will allow Turkey to buy fifth-generation F-35 fighters jets, there is renewed speculation the Turkish government could seek to buy warplanes from Russia instead.

Turkish President Recep Tayyip Erdoğan had ice cream with his Russian counterpart Vladimir Putin during a visit to Russia last week and had a look at Russian Sukhoi Su-35 and Su-57 jet fighter-bombers exhibited at the MAKS-2019 air show.

“Yes, you can buy it,” Putin said of the Su-57.

Erdoğan was later asked if he might be interested in purchasing the warplanes.

“Why not? We didn’t come here for nothing,” he responded.

But Turkish Foreign Minister Mevlüt Çavuşoğlu denied Turkey was actively looking to buy Russian Sukhois, insisting Turkey was still part of the F-35 programme. However, he reiterated that if Turkey ultimately could not buy the F-35s, it would look for alternatives, including Russian ones.

The United States blocked Turkey’s purchase of a fleet of F-35 jets and suspended it from the lucrative programme to help produce the aircraft after the Turkish government began to take delivery of the first components of S-400 air defence missiles from Russia in July.

U.S. Defense Secretary Mark Esper said the United States would only allow Turkey back into the F-35 programme if it moved its S-400s “out of the country”. The United States fears Turkey’s deployment of S-400s could allow Russia to gather sensitive data on the F-35’s defence capabilities.

Putin is suggesting Turkey could buy Sukhoi jets instead.

“We talked about cooperation on the Su-35 and the possible joint work on the new Su-57,” he said. “We have a lot of opportunities.

The Su-35 is a highly manoeuvrable multirole fighter-bomber. The Su-57 is a much newer fifth-generation stealth fighter, but there are only about 10 flyable Su-57 prototypes now in existence.

While Ankara has suggested that Russia could become an alternative source for modern fighter jets, Moscow has also proposed helping Ankara building its own fifth-generation TAI TF-X fighter by providing aircraft engines and electronic combat equipment.

Britain’s Rolls Royce was previously in talks to help Turkey develop an indigenous engine for the TF-X until it scaled back its efforts in March over fears that its intellectual property could be compromised. That led to speculation the U.S. company General Electric could help build the engines, but if U.S.-Turkey defence cooperation is further weakened, Russia could become an alternative.

There are many reasons to doubt Turkey would actually pursue close defence cooperation with Russia as it could trigger the United States to invoke the Countering American Adversaries Through Sanctions Act. CAATSA obliges Washington to impose sanctions on any country or entity that makes a significant purchase of military equipment from Russia.

Turkey has so far avoided CAATSA measures as a result of its $2.5 billion order of S-400 missiles, but further deals could push the U.S. administration to take action.

“I think it unlikely that Turkey will sign any new deals in the near future because such deals would trigger U.S. CAATSA sanctions, and I suspect Ankara would be keen to avoid further disrupting its relationship with the United States,” said Michael Kofman, director of the Russian Studies Program at CNA, a U.S. research and analysis organisation.

“Instead Turkey’s hope is that U.S. anger will subside over the S-400 deal and they might be in good graces by next year,” he said.

Kerim Has, a Moscow-based analyst on Russian and Turkish affairs, said Turkey’s purchase of the S-400 missiles was completely due to political reasons, rather than any defence need.

“Similarly, the political necessities might push Ankara to sign a warplane contract with Moscow,” he said. The Turkish military uses NATO weapons not compatible with Russian equipment, so purchasing Sukhoi jets would hardly be a logical decision, said Has.

“But under President Erdoğan, the Turkish military will likely become more dependent on Russia in both political and military terms to ensure Moscow’s support for Turkish political authorities in case a Maduro/Venezuela-type scenario emerges in Turkey,” Has said, referring to U.S. pressure on Venezuelan President Nicolas Maduro to step down.

There is little reason to believe though that Russia would supply Turkey with the technical know-how and cooperation it seeks to help build up its own indigenous arms industry.

“The question of technical assistance cannot be separated from one on arms sales, since there is no logical incentive for Russia to provide Turkey any technology unless it is part of a larger arms deal,” Kofman said.

Has also said Russia was not “going to be willing to transfer its critical technology experience and help to develop Turkey’s defence sector”.

Kofman doubted Ankara was serious about buying either Su-35s or Su-57s as both “are functionally different aircraft from the F-35 and are not optimised for the same missions, therefore Turkey is not going to buy them as an alternative, because they are not comparable in performance or purpose.”

Tom Cooper, an author and military aviation expert, said there was no realistic way in which the Su-57 could fulfil Turkey’s need for a fifth-generation fighter anytime soon.

“Technically, the Su-57 is not ready for service,” he said. “Industry-wise, it’s not even a semi-finished, but a dead-end project.”

This, he explained, was because the Russian Aviation Manufacturing Consortium (UAC) was unable to develop a new combat aircraft type. The loss of Ukraine, events in Russia over the last 20-30 years and Putin’s governance, he said, had resulted in Russia losing key technical know-how making it unable to “develop new engines and the necessary avionics. It lacks the money to even try”.

“Another issue is that the UAC is run by a board of directors hand-picked by Putin’s people, who have no clue about industrial management,” Cooper said.

“They can’t run a high-tech enterprise even in the modern-day Russian economic environment, not to talk about one that would be competitive on the international scene, they can’t organise research, and they can’t manage industrial production,” he said.

It was, therefore, no surprise that the Su-57 lagged years behind schedule “suffering from cost-overruns at the time it was unveiled in the public” back in 2010.

Cooper said it seemed as though someone in Russia had convinced themselves that all these problems could be solved through more money.

“That’s why they’ve attempted, for years, to secure Indian financing,” he said. But the UAC “is organised so that any possible foreign customers are held well outside the loop in regards of research and development.”

Foreign clients could not have direct influence on the aircraft’s capabilities, Cooper said.

“Unsurprisingly, the Indians eventually gave up trying: they’re not dumb to pay for something they do not need, and/or isn’t capable of doing things they would need to have,” he said. “Of course, in Turkey under Erdoğan, all of this doesn’t matter. Unsurprisingly, he got himself involved into apparently ‘serious’ negotiations for an acquisition of the Su-57.”

Joint production of the Su-57, Cooper said, was also unlikely due to the fact that the engines intended for the aircraft were about a decade behind schedule and the avionics suite is also “nowhere near complete, or even operational”.

Unless Russia and Turkey can find a solution to these major obstacles Cooper predicted “an utter mess in which nobody knows what the other side is doing, nor why.”