The 2,400-Kilometer Detour

On a grey road in Istanbul’s Fatih district, travellers haul heavy suitcases from a white bus carrying Iranian number plates. Among them are a husband and wife from Tehran who just finished a grueling three-day trip across the border. They took the 2,400-kilometer overland detour because their English-language exam had been cancelled at home due to sanctions, and the flights they hoped to catch kept disappearing from departure boards. As the husband, in a fleece jumper, explained their side of it: “We are affected by all this: the economy is terrible, and our Ielts exam was cancelled in Iran so we had to come here to take it instead.” His wife added on the pavement, “There were some flights available but they are constantly getting cancelled, so we decided to take the bus instead.”

Our listener asked whether U.S. Treasury Secretary Scott Bessent actually declared that every Iranian airline would be shut down worldwide by September 23, how that financial machinery works, and what happens to the planes.

Bessent did say it. On Monday before the deadline, he went on CNBC and issued an ultimatum: “On September 23, all the Iranian airlines will be shut down around the world.” Enforcement proponents argued that no global hub could risk U.S. access, and Bessent laid out that choice directly: “If they land, you cannot provide them with fuel, you cannot provide them with landing services, you cannot sell them tickets or you will be knocked out of the dollar system.” That broadcast rested on an official order issued earlier in the month, when the U.S. Treasury designated 27 Iranian airlines under Executive Order 13902 for operating in the nation's aviation sector.

This measure hit a massive flow of civilian travel. In 2025, according to Iran’s Civil Aviation Organization, over eleven million travellers took international routes, with nearly 7.2 million flying on Iranian carriers. Yet the fleet was already under severe strain before the latest cutoff, as scheduled international capacity had dropped sharply compared with the previous year.

This standoff has deep roots. Washington first imposed sanctions on Iran in November 1979 after the seizure of the American Embassy in Tehran, barred commercial aircraft and parts sales in 1995, and sanctioned Iran Air in September 2024 over arms transfers to Russia. Iranian Foreign Minister Abbas Araghchi condemned this escalation, remarking that after failing for decades, Washington’s only answer was more sanctions. Next, we look at how a threat issued in Washington translates into a fueling ban at an airport thousands of miles away.

The mechanism does not depend on American territory, American personnel, or even contracts drawn up in American dollars. Instead, secondary sanctions turn foreign businesses into enforcers by threatening their own survival. Under Treasury rules, foreign financial institutions that knowingly facilitate significant transactions for designated airlines risk strict conditions or outright prohibition on opening or maintaining correspondent or payable-through accounts in the United States. In everyday terms, losing those correspondent ties means being severed from U.S. dollar clearing entirely.

That clearing system is the quiet backbone of international flight operations. A commercial carrier cannot cross borders without airport slots, ground handlers, refueling contracts, ticketing platforms, and cross-border bank settlements. By making access to American financial plumbing conditional, Washington can project an extraterritorial no-fly zone without sending a single fighter jet into foreign airspace. As former senior Treasury sanctions official Kerri Bitsoff observed on the enforcement side, "These designations force a choice on every fuel supplier, ground handler, and bank that still touches an Iranian airline." No international airport authority or fueling consortium can easily afford to be knocked out of the dollar system over a refueling invoice.

What makes this move unprecedented is its sheer scope. Washington had previously placed targeted counterterrorism listings on individual carriers like Mahan Air, but late in August Treasury issued broad sectoral determinations under Executive Order 13902 targeting key areas including aviation. Treasury then designated Iran's remaining commercial carriers not already covered by U.S. sanctions, along with several foreign supporting entities. Scott Bessent delivered an explicit warning: "Let this be a warning to anyone doing business with Iran's remaining airlines, all of which we sanctioned today: You are at risk of being cut off from the global financial system." Rather than isolating specific aircraft, the administration moved to cut off every third-country commercial partner servicing an entire civil aviation sector.

The clock began running the moment those designations were filed. Alongside the new designations, the Office of Foreign Assets Control issued General License DD, granting a strict fifteen-day grace period to wind down previously authorized civil aviation dealings. That authorization expired at exactly 12:01 a.m. Eastern daylight time on September 23, 2026. Once that minute passed, any foreign handling agency, fueling truck, or settlement desk operating without specific American permission faced the immediate risk of secondary penalties. To see why the administration chose to drop that financial hammer at this exact moment, you have to look at the wartime intelligence that prompted the crackdown.

The trigger behind Washington's timing emerged on August 24, 2026, when the Treasury Department launched Operation Economic Outcast. A few days before the announcement, the Trump administration had promised an "economic D-Day," and Treasury Secretary Scott Bessent outlined five sectoral sanctions determinations under Executive Order 13902 targeting digital assets, technology, gold, shipping, and aviation. Bessent stated, "Our objective is to sever every economic lifeline that sustains this tyrannical regime until Tehran stands alone," adding, "any entity that facilitates money laundering on behalf of Iran will be removed from the U.S. dollar system."

Treasury framed its aviation crackdown around counter-proliferation and national security, alleging that Iran's commercial carriers operate as dual-use logistics lifelines for the Islamic Revolutionary Guard Corps. According to findings released on August 24 and September 8, Treasury asserted that ostensibly private airlines transport military personnel, weapons, and sensitive technology, while moving gold and cash to regional proxies. The administration also pointed to international sanctions from late 2024, when both the United States and the European Union designated Iran Air over allegations of transferring ballistic missiles and military drone components to Russia.

The immediate catalyst was what investigators uncovered regarding Mahan Air. Following earlier covert acquisitions—such as Boeing airliners routed from China to Cambodia via Indonesia before turning off transponders over Afghanistan—Treasury alleged that Mahan Air received at least three Boeing 777 aircraft through intermediary networks operating in the United Arab Emirates and Oman. When Treasury announced sanctions on foreign procurement networks, it cited entities across the UAE, Turkey, and the United Kingdom for allegedly facilitating the summer Boeing 777 trail. Yet Washington's counter-proliferation claims represent only one side of an escalating global dispute over commercial aviation.

That counter-proliferation argument, however, sits against a long and bitter dispute over passenger safety. Critics, international aviation bodies, and affected foreign partners argue that secondary sanctions violate the Chicago Convention by denying access to essential maintenance and parts, turning civilian aviation into a political battleground. Former Treasury Secretary Jacob Lew warned in 2016 that extraterritorial measures risk severe diplomatic strain and global economic instability, arguing they should be reserved only for exceptional circumstances. Those safety risks are not theoretical. A 2007 report from the International Civil Aviation Organization noted that aviation restrictions hindered critical repairs, while Iranian news reports cited seventeen crashes over twenty-five years that claimed about 1,500 lives.

For ordinary families, that mechanical isolation leaves scars. When Sepahan Airlines Flight 5915 suffered an engine failure shortly after takeoff from Mehrabad Airport, Akbar Mowlapasandi rushed between hospitals in search of his brother Alireza. "We didn’t know if he was among the wounded or the dead, so some of his colleagues and I divided into teams and started checking the hospitals where the wounded had been taken to," he remembered. "It was late afternoon when it became increasingly obvious my brother hadn’t made it." Tehran political observer Danial Rahmat argues that cutting off air corridors primarily penalizes everyday citizens. Meanwhile, reports noted that overland detours force elderly travelers and patients seeking medical care into grueling road journeys.

Yet despite the sweeping rhetoric of a worldwide shutdown, the ultimatum does not physically halt flights within Iran. American secondary sanctions hold legal jurisdiction only over foreign entities abroad, targeting international landing, dollar clearing, and refueling services rather than domestic airspace. Even though chronic parts shortages have historically left roughly half of Iran's civilian fleet grounded, domestic routes continue to fly between Iranian cities. The real crisis was not in the domestic skies, but on the international departure boards beyond Iran's borders as the September 23 deadline passed.

When you turn from the skies over Iran to the international departure boards, the pressure shifts outward. Proponents of enforcement argue that major foreign hubs simply cannot afford to defy Washington. As former senior Treasury official Kerri Bitsoff put it, these designations force a choice on every fuel supplier, ground handler, and bank that still touches an Iranian carrier. Treasury Secretary Scott Bessent had spelled out the consequence on television: service them, or get knocked out of the dollar system.

Faced with that choice, regional hubs pulled back almost immediately. On September 21st, Mahan Air announced it had suspended flights to Istanbul and Ankara at the request of Turkish authorities, while travel agencies reported the airline had lost access to Turkish ground handling. Azerbaijan Airlines announced a suspension of Iranian carrier flights starting September 22nd due to the new American aviation sanctions package. Then, on September 24th, Iranian media reported that the United Arab Emirates had cancelled all flights operated by Iranian airlines until further notice.

In Iraq, the standoff unspooled over seventy-two hours. Baghdad ordered its civil aviation authority to halt Iranian flights starting Wednesday, September 23rd. Iranian officials immediately tried to maneuver around the block. Majid Akhavan, spokesman for Iran's Civil Aviation Organization, said authorities were coordinating to redirect Baghdad flights to Najaf, where airport public relations official Muthanna Al-Talqani insisted scheduled flights to Iran were operating normally. But the reprieve was brief. By Friday, September 25th, Najaf suspended Iranian flights at two in the morning, leaving all four Iraqi international airports serving Iran completely closed to its aircraft.

The legal net left foreign airport managers little room to argue. As Kerri Bitsoff observed, international aviation relies so thoroughly on American-origin technology that the rules reach nearly the entire global fleet. Aircraft and parts manufactured outside the United States fall under American jurisdiction if they contain more than 10 percent U.S. content. Servicing those planes abroad exposes foreign crews to direct export enforcement. Yet even as Western and regional departure boards went dark, Iranian planes were already turning toward exceptions that kept moving east.

Even as departure boards went dark across the Middle East, the view looking east was entirely different. Skeptics of Washington's enforcement reach point to Beijing, where Chinese Foreign Ministry spokesman Guo Jiakun said that "China consistently opposes illegal unilateral sanctions that lack a basis in international law or authorisation from the UN Security Council." On September 23, monitoring data showed a Mahan Air jet from Tehran successfully touched down in Guangzhou, even though the flight was not listed on the airport's official website. Tracking showed at least six flights departing Iran after the restrictions took effect, heading to destinations including Shanghai, Bangkok, Phuket, and Kabul.

That defiance reflects both political alignment and operational adaptation. Analyst Saj Ahmad noted that strategic partners like China and Pakistan are simply not going to fold on matters like this, predicting Beijing and Moscow would broadly ignore the demands. Operationally, regional analysts argue that carriers can adapt by flying with extra fuel onboard to bypass foreign refueling bans, while an importer in Tehran observed that sanctions cannot completely halt business when transactions flow through networks of small, medium-sized currency traders.

Yet those workarounds run into hard limits. Ahmad pointed out that "it's hard to see who will play ball and just how the US will enforce this if people simply ignore these demands," while Middle East Institute fellow Alex Vatanka framed the lingering uncertainty as how strongly Washington will insist on enforcement and what other countries will decide, alongside broader questions over whether alternative non-dollar arrangements can hold. The total net decline in flight volumes across the sector remains unmeasured, and shadow schemes like the summer Boeing 777 trail cannot easily solve the relentless Western parts bottleneck. For ordinary citizens cut off from regional hubs, the fallback remains the 2,400-kilometer overland detour to Istanbul, where coach fares rose to 2,000 Turkish lira, about 41 dollars, as ticketing agent Arqavan explained that higher fuel prices forced ticket costs up.

Scott Bessent's warning was unequivocal: he delivered that explicit ultimatum on CNBC, cautioning foreign airports that servicing Iranian planes meant being knocked out of the dollar system. In practice, the threat paralyzed Iranian commercial routes across the Gulf, the Caucasus, and Turkey, but it did not halt domestic flights inside Iran, nor did it close the defiant corridors running east into Asia.