The US Treasury Department sanctioned 27 Iranian airlines on September 8 in a 36-entity package — the extraterritorial lever behind Tehran's threat two weeks later to "paralyse" airports in any country that helps ground Persian Gulf aviation.

Mohsen Rezaei, Secretary of Iran's Supreme National Security Council, delivered the warning on state television on September 23, 2026. Iran, he said, would prevent neighboring airports from functioning if their governments cooperated with Washington's campaign to stop Iranian flights, Reuters reported.

The threat landed precisely on the US-imposed deadline. Iran's Civil Aviation Organization told carriers that Baghdad and Muscat airports would stop accepting Iranian services from midnight on September 23. Spokesman Majid Akhavan said officials were redirecting Baghdad-bound traffic to Najaf International Airport — a smaller Iraqi gateway now absorbing flows that previously fed Baghdad International.

How much of the network fell offline?

Georgia and Azerbaijan separately confirmed suspending Iranian flights in the days around the deadline. A Tehran travel agent told AFP that Qatar services had been dropped as well, narrowing Tehran's Gulf reach to airports willing to absorb secondary-sanctions risk.

The squeeze was US-engineered. Treasury Secretary Scott Bessent said on September 21 that the threat of sanctions against aviation service providers would force Iranian airlines to halt operations beginning September 23.

What is still flying?

Restrictions did not close every corridor. Flightradar24 data showed a Mahan Air service from Tehran landed in Guangzhou after the deadline — a symbolically significant arrival given Guangzhou's role as the most-used Chinese gateway for Iranian-linked operators. Another Mahan service to Shanghai remained scheduled. Some Istanbul flights still appeared on timetables, even as other Turkish routes were canceled. China has publicly opposed the US measures, leaving Chinese airports open in a way that Baku, Tbilisi and Doha are not.

That asymmetry — a Beijing-Moscow axis versus a contracting Caucasus-Gulf arc — now defines where Iranian-flag capacity can still land.

What is the legal mechanism?

Washington is targeting the foreign companies Iranian carriers depend on to operate abroad, replicating on aviation the model Treasury used against Iran's fuel-import network. Businesses that continue to support sanctioned carriers — cargo handlers, sales agents and ground service providers — themselves face sanctions exposure.

A temporary general license that had allowed previously permitted transactions to wind down expired at 00:01 Eastern Daylight Time on September 23. Operators still holding pre-sanctioned lease payments, maintenance contracts or spare-parts shipments lost their safe harbor at that minute, eliminating the last regulatory cushion for third-party service providers.

The September 8 designation accused Iran of using its civil aviation industry to transport weapons and personnel and to acquire aircraft and equipment through overseas intermediaries — language designed to harden compliance at third-party MROs, fuel suppliers and insurance brokers.

Can Tehran deliver on the counter-threat?

The mechanism is opaque. Iran did not specify how it would paralyse airports that refuse Iranian flights, and Tehran's direct leverage over Iraqi, Omani, Georgian and Azerbaijani airport operations is structurally limited. The threat nevertheless raises the cost of compliance for neighbors already weighing US secondary-sanctions exposure against Iranian retaliation.

For carriers, the operational verdict is mixed: legacy hubs in Iraq, the Caucasus and the Gulf are off-limits or in transit, while the eastern corridor to China and a residual Istanbul lifeline remain open. The next data points are October ticket-sales out of Najaf, the disposition of Mahan's remaining western wet-lease exposure and whether any further neighbor joins the blacklist before mid-autumn.