Turkey’s F-35 Deal Stalls as Efforts to Offload Russian S-400 Systems Freeze

Turkey was removed from the F-35 programme in 2019 after taking delivery of the Russian-made S-400 Triumf system. Six F-35s had already been produced and paid for by Ankara, but they have remained in the United States ever since.

The problem is not simply political distrust. US law and the security architecture surrounding the F-35 make the continued presence of the S-400s in Turkey incompatible with Ankara's return to the programme.

The concern is that sophisticated Russian radar and air-defence technology operating alongside the F-35 could create unacceptable risks to the aircraft's sensitive capabilities and data. The F-35 is built around technological advantages that depend not only on the aircraft itself but on protecting information about how it operates and how it is detected.

That makes the S-400 an unusually stubborn obstacle. Turkey cannot simply promise to operate the two systems separately and expect Washington to accept the arrangement.

The legal barrier is equally important. CAATSA sanctions legislation imposes restrictions on significant transactions involving Russia's defence sector, while US requirements governing the F-35 prevent access for a state that continues to operate or house the S-400.

Trump's political support therefore does not translate automatically into a sale.

Senate Foreign Relations Committee Chairman Jim Risch has described the transaction as being at a “standstill”, while Senator Rick Scott has said the administration has yet to provide a route forward that avoids full divestment of the Russian systems.

The result is an unusual situation: the White House wants to revive a defence relationship with a major NATO ally, but Congress retains the ability to prevent the transaction from moving ahead.

The buyer that does not want the problem

Turkey's preferred solution was not to destroy the S-400s but to move them elsewhere.

Negotiations that began around July over a possible sale to the UAE have, however, stalled. The reason is revealing. Abu Dhabi has its own interest in acquiring F-35s, and taking possession of the Russian systems could expose it to the same US sanctions and technological restrictions that have trapped Ankara.

The secondary market has therefore reproduced the original problem.

A country that wants access to the most advanced US combat aircraft has little incentive to acquire a Russian strategic air-defence system that could jeopardise that access. The S-400 may be a valuable military asset in isolation, but its political and technological liabilities become part of the package.

There is another complication. Russia retains a say over any transfer. Under the terms governing the export of the system, Turkey cannot simply sell the S-400 to a third country without Moscow's approval. Russian Foreign Minister Sergey Lavrov has reiterated that requirement publicly.

That gives Moscow an unusual form of continuing leverage over a defence acquisition made years ago.

Even if Washington and Ankara agree on the political principle of removing the S-400, Turkey cannot necessarily decide on its own where the system goes next.

When disposal becomes a strategic decision

That leaves Ankara considering options that would have seemed extraordinary when it purchased the system: disabling the S-400s, permanently removing them from service, or dismantling and destroying them for scrap.

The prospect of destroying expensive military hardware illustrates how deeply the 2019 decision has altered the economics of Turkey's defence policy.

The S-400 was acquired as a major strategic capability. Yet the same system now stands between Turkey and the Western fighter programme it needs to modernise its air force. Ankara has already paid for six F-35s that it cannot take possession of. It could now face the additional cost of effectively writing off the Russian system in order to regain access to the Western one.

This is not simply a procurement failure. It is the cost of incompatibility between defence architectures.

For years, middle powers have sought flexibility by buying equipment from competing suppliers. Turkey's experience is showing how difficult that strategy becomes when weapons systems are tied to wider networks of intelligence, software, data security and operational interoperability.

A modern fighter is not an isolated platform. Neither is an advanced air-defence system.

Washington's problem is bigger than the S-400

The congressional resistance also cannot be reduced to technical concerns.

US lawmakers have additional reservations about Turkey's foreign policy, including its relations with Hamas, Iran and Russia, as well as disputes involving Cyprus and Greek airspace and concerns over domestic governance. The S-400 provides the clearest statutory barrier, but it sits inside a much broader argument about whether Ankara remains sufficiently aligned with Washington's strategic priorities.

That makes Trump's effort to revive the F-35 relationship politically difficult.

For the administration, restoring the sale could strengthen ties with an important NATO member and reinforce Turkey's role in the alliance. For congressional opponents, however, making an exception after the S-400 purchase could weaken the principle that sensitive defence technology comes with conditions that cannot be negotiated away for political convenience.

Israel's opposition adds another layer.

Prime Minister Benjamin Netanyahu has warned that transferring F-35s to Turkey would upset the regional balance of power. Israel already operates the aircraft in the Middle East, and Turkish access would alter the distribution of advanced air power in a region where military technology is closely connected to political influence.

Congressional debate is therefore taking place at the intersection of three interests: protecting the F-35's technological security, enforcing US sanctions policy and managing the regional balance of power.

NATO's technological fault line

The deeper significance of the dispute lies in what it says about the future of defence procurement.

The traditional idea that a country can diversify its suppliers without fundamentally choosing a geopolitical camp is becoming harder to sustain at the highest end of military technology. The more sophisticated the systems, the more tightly they are connected to secure communications, intelligence, software and operational standards.

That creates a form of technological balkanisation.

Turkey's predicament is an especially stark example because it is a NATO member seeking access to the alliance's most sophisticated Western combat aircraft while retaining a Russian strategic air-defence system. The UAE, despite not being in the same position institutionally, is confronting a similar procurement dilemma: acquiring the S-400 could complicate its own ambitions for the F-35.

The lesson for countries pursuing a hedging strategy is uncomfortable. Defence equipment can outlive the diplomatic assumptions under which it was purchased.

Russia does not need to regain control of Turkey's defence policy to retain influence over the S-400 issue. Washington does not need to impose a new embargo to keep Ankara outside the F-35 programme. Congress can enforce the existing legal framework, while Moscow's contractual position constrains Turkey's alternatives.

And Israel can influence the debate simply by arguing that a Turkish F-35 fleet would alter the regional balance.