US Treasury Secretary Scott Bessent has warned that Iranian airlines could be effectively shut out of international operations from September 23 as Washington expands its sanctions campaign against Tehran.

Bessent said foreign airports and companies that continue servicing Iranian carriers could face secondary sanctions. This could include providing aircraft fuel, landing and ground services, or selling tickets for Iranian airlines.

“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 measures would not automatically close foreign airspace to Iranian aircraft, but could make international operations increasingly difficult by restricting access to essential aviation and financial services.

The practical impact will depend on how airports, fuel suppliers, financial institutions and governments around the world respond to the US sanctions threat.