US limits air defence time slots for tankers sailing through Hormuz

September 12, 2026 adminsr

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The US has asked tankers travelling through the Strait of Hormuz to sail only at specific times to guarantee military protection after Iran stepped up attacks on ships travelling at night.

Washington has been offering air-based defence since May to ships wanting to sail via a route hugging the Omani coast on the strait’s southern side, in an effort to defy Iranian attacks and keep some oil flowing out of the Gulf.

Shipowners had to apply to the US naval co-ordination centre (Naval Cooperation and Guidance for Shipping, or NCAGS), which then gave mariners co-ordinates to follow and permission to sail through during broad time windows overnight, during which they would be protected by US aircraft.

That period was cut down to two specific time slots daily around the start of September, according to emails sent by NCAGS to maritime advisers seen by the FT. Vessels have been told to start their journey at specified times, such as 9am.

“We are now providing recommended transit times that vary by day. Your vessel is not required to go during these times, but it is encouraged in order to receive the best support,” one email said.

“Transiting during a period of darkness has not proven to be the most secure time of day,” given threats to merchant shipping, it said in another.

US Central Command (Centcom), which oversees Washington’s military operations in the Middle East, said the NCAGS messages spoke for themselves.

Iranian forces have attacked dozens of vessels trying to pass through the contested waterway in an effort to assert control since the US and Israel attacked Iran in February.

The adjustment of US support to specified times of the day or night has come just as both sides stepped up their attacks on commercial shipping.

Iran said early on Wednesday that it had targeted two US vessels and eight oil tankers in response to American strikes on five Iranian tankers.

Those attacks came in response to the Islamic Revolutionary Guard Corps targeting an American warship with ballistic missiles early in the week, the US military said.

Further Iranian attacks on tankers just off the coast of Dubai and Iraq were reported by UK Maritime Trade Operations on Wednesday.

Joshua Tallis, naval analyst at the US security research organisation CNA, said the request for ships to transit at specific times was likely “an effective means to manage the costs associated with a persistent and indefinite US defence of the southern Strait of Hormuz route”.

Tallis said it can cost anywhere from $25,000 to $75,000 to fly an advanced US military aircraft for one hour.

Concentrating resources into smaller time slots rather than a 12-hour period overnight would mean that the US had “more military capability in order to protect better”, said a maritime security adviser working with ships in the Gulf.

Transiting the strait takes around seven hours for a commercial ship going at slow to moderate speed. The IRGC has been known to send out small patrol boats to try to detect ships using the Omani route, which usually travel at night with their GPS signals and lights off.

More than 70 commercial vessels have been attacked since the conflict began on February 28.

Iran on Monday said it planned to introduce a “restricted zone” in the strait. Mohsen Rezaei, head of the country’s Supreme National Security Council, said this zone would “begin from the line of the US naval blockade, extend towards the Strait of Hormuz, and from this side continue into the Persian Gulf”.

Any ship sailing into that zone would be subject to “sanctions”, Tehran said, although it has not spelled out what these would involve.

It also said a preliminary agreement with Oman over the future management of the strait was close to being finalised. But shipbroker Clarksons said on Monday that it still did not expect the disruption to traffic through the waterway to ease until at least the second half of 2027.

Retired vice admiral John Miller, who formerly commanded US naval forces in the Middle East, said of the schedule change: “As we settle in for something that could be a process that we’re doing for a while, it’s going to be important to husband the assets in a way that allows us to be able to sustain the activity.”

Providing air cover 24/7 “would be really hard to do over an extended period of time” so the US is “going to have to put some guidelines on it”, he added.

Cartography by Cleve Jones and Andrew Francisco