At least 42 United States military aircraft, including fighter jets and drones, were lost or damaged in the country’s war on Iran, a study recently published by the US Congressional Research Service said.The study published on May 13 is based on news reports, and statements made by the US Department of War and the US military. It added a caveat that the number is subject to revision because of “classification, ongoing combat activity and attribution”.The aircraft that were lost include four F-15E Strike Eagle fighter jets, three of which were shot down on March 2 in what the US military described as “friendly fire incidents” over Kuwait.The fourth was shot down on April 5 during combat operations over Iran. The crew members flying this aircraft had been rescued by US forces from inside Iran.Other aircraft that were lost include one F-35A Lightning II fifth-generation fighter jet, one A-10 Thunderbolt II ground-attack aircraft, seven KC-135 Stratotankers that are used for aerial refuelling, one E-3 Sentry Airborne Warning and Control System aircraft and two MC-130J Commando II special operations planes.The list also mentioned the reported loss of 24 MQ-9 Reaper drones, one MQ-4C Triton drone and one HH-60W Jolly Green II helicopter.The US Department of War’s cost estimate for the operations in Iran had increased to $29 billion, the study noted. “A lot of that increase comes from having a refined estimate on repair or replacement costs for equipment,” it quoted Pentagon’s finance chief Jules W Hurst III as having told a Senate committee on May 12.While it was unclear how many of the aircraft had been shot down, targeted on the ground or had been lost in accidents, Iranian Foreign Minister Abbas Araghchi on Wednesday shared the study on social media and claimed that “our powerful armed forces are confirmed as 1st to strike down a touted F-35”.The F-35A is a stealth fighter jet that is considered among the most advanced combat aircraft in the world.Araghchi also stated that the study was an acknowledgment by the US Congress of billions of dollars worth of losses. “With lessons learned and knowledge we gained, return to war will feature many more surprises,” he said.The Congressional Research Service is a public policy research arm that provides policy and legal analysis to the US Congress and its committees. The study is not the position of the US military or the White House.The costly warThe study comes as a fragile ceasefire continues to hold between the US and Iran.The US and Israel launched an attack on Iran on February 28, claiming that Tehran’s action posed an existential threat to Israel. Washington acts as a guarantor of Israel’s security. Iran retaliated by striking Israel and US military bases in the region, targeting major cities in Gulf countries and ships.Tehran also effectively blocked the Strait of Hormuz, the narrow waterbody connecting the Gulf to the Arabian Sea, for most international commercial vessels, triggering a global energy crisis. About 20% of global petroleum supply passes through the maritime chokepoint.The peace talks between Iran and the US that were held in Islamabad, Pakistan collapsed on April 12 but the ceasefire in the region had largely held so far. However, on Monday, US President Donald Trump told reporters that the truce was on “massive life support”.Israel has been claiming that Iran is close to obtaining a nuclear weapon, which could alter the regional security balance. Tehran has long maintained that its nuclear programme is for civilian purposes.Written by Sara Varghese. Edited by Nachiket Deuskar.Also read: Why ‘shooting down’ fighter jets has become central to narrative setting