31 CFR §560.529

1. (a)Except as provided in paragraph (b) of this section, goods or services provided in the United States to a non-Iranian carrier transporting passengers or goods to or from Iran are permissible if they are:
   1. (1)Bunkers or bunkering services;
   2. (2)Supplied or performed in the course of emergency repairs; or
   3. (3)Supplied or performed under circumstances which could not be anticipated prior to the carrier's departure for the United States.
2. (b)This section does not authorize the provision of goods or services in connection with the transport of any goods to or from the Government of Iran, an Iranian financial institution, or any other person whose property and interests in property are blocked pursuant to § 560.211.