The U.S. military has reduced recommended escort-support transit windows for merchant ships in the Strait of Hormuz to two per day, according to the Financial Times, as a prolonged confrontation with Iran increases operational and financial pressures. The U.S. Navy’s Naval Cooperation and Guidance for Shipping, or NCAGS (a unit coordinating with commercial shipping), notified maritime officials that the limit had applied since early September. Ships are not required to use the windows, but NCAGS recommends them for the strongest available support. Since May, the U.S. military has provided air-defense support for merchant vessels traveling along Oman’s coast south of the strait, seeking to deter Iranian attacks and limit disruption to Gulf oil shipments. Iran said it attacked 10 ships near the strait on September 9, reportedly the largest assault on commercial vessels since the war began, while about 70 merchant ships have been attacked by Iran since February. Joshua Tallis, a researcher at CNA, the Center for Naval Analyses, said advanced U.S. military aircraft cost $25,000 to $75,000 an hour to operate. Experts said the reduced schedule is intended to manage the long-term expense of defending shipping lanes.