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The US is threatening to ground every Iranian airline operating outside the country starting Wednesday by going after the foreign companies and countries that keep them flying.

Getting into it: Treasury Secretary Scott Bessent said Monday on CNBC that “on September 23, all the Iranian airlines will be shut down around the world,” with the threat aimed at airports, fuel suppliers, ground handlers, and ticketing companies rather than the carriers themselves. According to Bessent, the US will not physically stop any planes but will punish any foreign business that continues servicing Iranian carriers.

“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,” Bessent said.

The deadline follows a Treasury action earlier this month that sanctioned 36 targets tied to Iran’s aviation sector, including all 27 remaining active Iranian airlines that had not already been hit, among them Qeshm Air, Iran Aseman, Zagros, and Kish. The Treasury also went after front companies and middlemen in the UAE, Turkey, Malaysia, and Kazakhstan accused of helping Mahan Air, which the US has designated since 2011 over its ties to the Islamic Revolutionary Guard Corps, obtain US-made aircraft and move cargo.

The moves fall under Bessent’s “Operation Economic Outcast,” the campaign he announced back in August to choke off Iran’s remaining sources of cash. Even before the campaign, years of sanctions had already screwed Iran’s airlines, cutting them off from new planes, parts, and maintenance.

As of now, Iranian officials have not publicly commented on the threat.