31 CFR §515.420

The prohibition on dealing in property in which Cuba or a Cuban national has an interest set forth in § 515.201(b)(1) includes a prohibition on the receipt of goods or services in Cuba, even if provided free-of-charge by the Government of Cuba or a national of Cuba or paid for by a third-country national who is not subject to U.S. jurisdiction. The prohibition set forth in § 515.201(b)(1) also prohibits payment for air travel by a person subject to U.S. jurisdiction to Cuba on a third-country carrier unless the travel is pursuant to an OFAC general or specific license.