On the eve of new U.S. sanctions targeting Iranian aviation, Iran Air said it had not received any official orders from Turkey, Azerbaijan, or Iraq to stop flying to Istanbul, Baku, or Najaf. However, airports, service providers, and travel agencies have already begun limiting their cooperation with Iranian airlines, reflecting the impact of the sanctions. Iran Air emphasized that its flight schedules would remain unchanged unless it received formal instructions from the relevant aviation authorities. U.S. Treasury Secretary Scott Bessent announced that starting September 23, Iranian airlines would lose access to essential services needed for their international operations. He warned that if Iranian airlines landed at foreign airports, local entities would not be able to provide them with fuel, ground support, or sell tickets without risking exclusion from the dollar financial system. The U.S. sanctions do not automatically close foreign airspace but instead aim to disrupt the commercial and financial services that Iranian carriers rely on. On September 8, the Office of Foreign Assets Control (OFAC) sanctioned 36 entities linked to Iran's aviation sector, including 27 active airlines that had not previously been targeted. The U.S. administration claims that Iran's aviation sector is used to transport weapons, people, and illegal goods, as well as to acquire Western-origin aircraft and technology through hidden companies. OFAC's focus includes the movement of aircraft, cargo support, commercial representation, and supply chains. The U.S. Treasury warns that foreign financial institutions that do significant business with sanctioned entities could face secondary sanctions and lose access to the U.S. financial system. The effects of the sanctions are being felt immediately, even when a country does not explicitly ban flights. Airports, fuel suppliers, ground crews, catering services, and ticket sales systems may stop working with airlines exposed to U.S. sanctions. Disruptions have already occurred: Mahan Air, an Iranian private airline under sanctions, stopped flying to Turkey at the request of Turkish authorities. In Georgia, flights by sanctioned Iranian airlines were banned since September 21. Azerbaijan suspended Iranian flights starting September 22. In Iraq, despite no official order from Iran Air to stop flights to Najaf, Baghdad Airport no longer accepts Iranian flights. In Oman, Iranian media reported restrictions on flights to Muscat. A major travel agency in Tehran now stops selling tickets to Baghdad, Muscat, Qatar, Georgia, and Azerbaijan, due to fears of last-minute cancellations. Iran has 27 airlines, but most operate mainly within the country. Iran Air and Mahan Air are among the most important carriers on international routes, relying on neighboring countries such as Turkey, Iraq, Azerbaijan, Oman, and the United Arab Emirates, as well as some routes to China and Russia. However, these foreign connections are becoming harder to maintain as local service providers fear being cut off from the dollar financial system. The effects of the sanctions are not uniform. On September 23, several Iranian flights continued to Asia, including to Bangkok, Phuket, Shanghai, and Kabul, according to flight tracking data. Mahan Air also landed a plane in China on the same day. However, uncertainty remains high, as Iran Air can still operate to a destination as long as the local authority does not object. In practice, flights depend on a global network of services—fueling, maintenance, payments, ticket sales, and insurance—that the U.S. sanctions are trying to weaken. The current crisis follows several months of regional tensions that have already heavily impacted air traffic. Israeli-American strikes against Iran in late February led to the complete closure of Iranian airspace, which has since partially reopened, but opportunities to leave or enter the country have significantly decreased.