The United States began fully enforcing a secondary boycott (sanctions on companies supporting a target) against 23 Iranian airlines on the 23rd, barring refueling, landing services and ticket sales while warning violators they could lose access to the dollar settlement system. Scott Bessent, the U.S. Treasury Secretary, said in a CNBC interview on the 21st that Iranian aircraft should receive none of those services. The U.S. Treasury Department sanctioned agents of Mahan Air, Iran's largest private airline, and designated 27 Iranian airlines as additional sanctions targets. The Trump administration says Iran uses civilian flights to move weapons and combatants; Mahan Air was previously sanctioned in 2011 over alleged transport of Iranian military personnel and weapons. Flight suspensions and airport restrictions have spread across Iraq, Oman, Turkey, Azerbaijan and Georgia, although Iran Air said it had received no official notices from Turkish, Azerbaijani or Iraqi aviation authorities. China and Russia are not joining the sanctions, and China denounced unilateral measures lacking international-law or UN Security Council authorization. The restrictions add pressure to an Iranian economy already affected by a maritime blockade, disrupted cargo routes, inflation, a weaker rial and shortages of essential goods. Analysts cited in the source say Iranian carriers could eventually be confined largely to domestic routes, while the effect of the new measures remains uncertain because the industry has faced sanctions for years.