Amid heightened tensions following the 19 June downing of a US Navy unmanned aircraft system by the Iranian military over the Persian Gulf, the US Federal Aviation Administration has banned all US carriers from operating within the Tehran FIR over the waters of the Persian Gulf and Gulf of Oman (highlighted area pictured below).

Area of Iranian FIR US aircraft are prohibited from
The green highlighted area shows the portion of the Tehran FIR from which US carriers are now prohibited

Notam text

The FAA issued the following Notam at 01:48 UTC on 21 June.

KICZ   INTERNATIONAL SECURITY
A0019/19 (Issued for KICZ PART 1 OF 2) - SECURITY..UNITED STATES OF AMERICA PROHIBITION AGAINST CERTAIN
FLIGHTS IN THE OVERWATER AREA OF THE TEHRAN FLIGHT INFORMATION
REGION (FIR) (OIIX) ABOVE THE PERSIAN GULF AND GULF OF OMAN ONLY.
ALL FLIGHT OPERATIONS IN THE OVERWATER AREA OF THE TEHRAN FLIGHT
INFORMATION REGION (FIR) (OIIX) ABOVE THE PERSIAN GULF AND GULF OF
OMAN ONLY ARE PROHIBITED UNTIL FURTHER NOTICE DUE TO HEIGHTENED
MILITARY ACTIVITIES AND INCREASED POLITICAL TENSIONS IN THE REGION,
WHICH PRESENT AN INADVERTENT RISK TO U.S. CIVIL AVIATION OPERATIONS
AND POTENTIAL FOR MISCALCULATION OR MIS-IDENTIFICATION. THE RISK TO
U.S. CIVIL AVIATION IS DEMONSTRATED BY THE IRANIAN SURFACE-TO-AIR
MISSILE SHOOT DOWN OF A U.S. UNMANNED AIRCRAFT SYSTEM ON 19 JUNE
2019 WHILE IT WAS OPERATING IN THE VICINITY OF CIVIL AIR ROUTES
ABOVE THE GULF OF OMAN.
A. APPLICABILITY. THIS NOTAM APPLIES TO: ALL U.S. AIR CARRIERS AND
COMMERCIAL OPERATORS; ALL PERSONS EXERCISING THE PRIVILEGES OF AN
AIRMAN CERTIFICATE ISSUED BY THE FAA, EXCEPT SUCH PERSONS OPERATING
U.S.-REGISTERED AIRCRAFT FOR A FOREIGN AIR CARRIER; AND ALL
OPERATORS OF AIRCRAFT REGISTERED IN THE UNITED STATES, EXCEPT WHERE
END PART 1 OF 2. 21 JUN 01:48 2019 UNTIL PERM. CREATED: 21 JUN 02:00 2019
A0019/19 (Issued for KICZ PART 2 OF 2) - THE OPERATOR OF SUCH AIRCRAFT IS A FOREIGN AIR CARRIER.
B. PERMITTED OPERATIONS. THIS NOTAM DOES NOT PROHIBIT PERSONS
DESCRIBED IN PARAGRAPH A (APPLICABILITY) FROM CONDUCTING FLIGHT
OPERATIONS IN THE ABOVE NAMED AREA WHEN SUCH OPERATIONS ARE
AUTHORIZED EITHER BY ANOTHER AGENCY OF THE UNITED STATES GOVERNMENT
WITH THE APPROVAL OF THE FAA OR BY A DEVIATION, EXEMPTION, OR OTHER
AUTHORIZATION ISSUED BY THE FAA ADMINISTRATOR.  OPERATORS MUST CALL
THE FAA WASHINGTON OPERATIONS CENTER AT 202-267-3333 TO INITIATE
COORDINATION FOR FAA AUTHORIZATION TO CONDUCT OPERATIONS.
C. EMERGENCY SITUATIONS. IN AN EMERGENCY THAT REQUIRES IMMEDIATE
DECISION AND ACTION FOR THE SAFETY OF THE FLIGHT, THE PILOT IN
COMMAND OF AN AIRCRAFT MAY DEVIATE FROM THIS NOTAM TO THE EXTENT
REQUIRED BY THAT EMERGENCY.
THIS NOTAM IS AN EMERGENCY ORDER ISSUED UNDER 49 USC 40113(A) AND
46105(C).
ADDITIONAL INFORMATION IS PROVIDED AT:
HTTPS://WWW.FAA.GOV/AIR_TRAFFIC/PUBLICATIONS/US_RESTRICTIONS/. SFC - UNL END
PART 2 OF 2, 21 JUN 01:48 2019 UNTIL PERM. CREATED: 21 JUN 02:00 2019

Practical effects

Very few US carriers operate flights through the Tehran FIR and less than a handful of those cross the now prohibited areas. Flights that do are generally cargo operators. Earlier on June 20 United Airlines canceled its service returning to New York (EWR) from Mumbai and has canceled flights on the route until further notice. While the flight does not usually pass over the prohibited area, United said a thorough safety and security review prompted its actions. UA48 and UA49 both regularly transit overland portions of the Tehran FIR (see below).

Usual route of UA48 and UA49
Usual routing of UA48 and UA49 through Iranian airspace

The real effects may felt if carriers in other countries decide to follow the FAA prohibition or if other national authorities issue their own prohibitions.

Background on Iranian airspace

In 2014, security concerns above Iraq prompted much of the traffic between the Gulf states and Europe and North America to begin transiting Iran. In November 2017, Iraqi airspace reopened to transiting traffic, pulling in traffic that had previously transited Iran. The below images show the regional airspace in on 21 June from 2017, 2018, and 2019.

June 2017 June 2018 June 2019
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There are a few changes worth noting. From 2017 to 2018, the concentration of transiting flights to and from Europe/North America between the big 3 hubs—Dubai, Doha, Abu Dhabi—shifts from Iran to Iraq. From 2018 to 2019 flights that previously transited Pakistan, Afghanistan, and Turkmenistan now primarily route through Iran due to the continued airspace restrictions put in place by Pakistan. This has also pushed much of the transiting traffic south, nearer to the area now prohibited to US carriers.

This is a developing story and updates will be posted in this post as necessary.
 

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