The US Treasury’s sanctions on additional Iranian airlines threaten permanent damage to an already badly bruised industry, all but severing the country’s limited air connections to the rest of the world. The Trump administration on Tuesday added several Iranian airlines and outside companies to its sanctioned entities list, and warned financial institutions about the risks of dealing with the sector, which it said helped Tehran procure weapons components. The economic impacts are difficult to measure; last year, Iran Air’s chief executive said the industry added 9% to the country’s GDP of about $300 billion, and there is no official data on how that has changed since Israel and the US launched attacks on Feb. 28. But the sanctions will further isolate a country already difficult for many airlines and cargo companies to reach. The latest sanctions “could all but shut down Iran’s air connectivity with the outside world,” said Farhad Alavi, a partner at Akrivis Law Group in Washington DC.

The moves follow measures last month against two banks outside Iran: Egypt’s Banque Misr UAE branches and Golden Global Investment Bank in Turkey. In a statement, the US Treasury said it had sanctioned 36 entities “for supporting Iran’s aviation sector, which the regime uses to move weapons, personnel, and illicit cargo.”

Iran’s aviation industry has been saddled with sanctions since the late 1970s. The average age of in-service aircraft in the country is about 42.2 years, according to data from aviation consultancy Cirium — more than double the industry standard for pulling “old” planes from the fleet. Airlines often cannibalize parked planes for spare parts as Boeing and Airbus SE can’t easily sell there. Iranian airlines ordered about $40 billion worth of planes from western companies during a short-lived sanctions relief window under the 2016 JCPOA agreement - 100 from Airbus, 120 from Boeing and 20 from ATR. Deliveries were halted after President Donald Trump pulled out of the nuclear pact with only 16 aircraft delivered.

“Their sector had basically no life in it. They didn’t have the infrastructure, they didn’t have the basic capabilities. There’s nothing left of this sector,” said Richard Aboulafia, Managing Director at Aero Dynamic Advisory. Foreign air connectivity was limited to just a few airlines before the war and is now nonexistent, as all international and regional airlines have suspended operations to Iran after Feb. 28.

Iran’s biggest airport and its main international hub, Imam Khomeini Airport in Tehran, still has some foreign arrivals and departures scheduled via local airlines. Istanbul stands out as the most common destination, alongside Baghdad, Shanghai, Muscat, Dubai, Tbilisi and others. But policing sanctions non-compliance could be challenging on its own, as countries with ties to Tehran have so far shrugged off the recent threats.

“Much of Iran’s aviation industry is already heavily sanctioned, so the effect will be limited. But it will dissuade those limited airlines from still flying to Iran or it will lead to price increases if they do. The result once again is that ordinary Iranians keep getting squeezed,” said Dina Esfandiary, Bloomberg Middle East Geoeconomics analyst.