The main Iraqi air effort had shifted to the destruction of Iranian war-fighting capability (primarily Persian Gulf oil fields, tankers, and Kharg Island), and starting in late 1986, the Iraqi Air Force began a comprehensive campaign against the Iranian economic infrastructure. By late 1987, the Iraqi Air Force could count on direct American support for conducting long-range operations against Iranian infrastructural targets and oil installations deep in the Persian Gulf. U.S. Navy ships tracked and reported movements of Iranian shipping and defences. In the massive Iraqi air strike against Kharg Island, flown on 18 March 1988, the Iraqis destroyed two supertankers but lost five aircraft to Iranian F-14 Tomcats, including two Tupolev Tu-22Bs and one Mikoyan MiG-25RB. The U.S. Navy was now becoming more involved in the fight in the Persian Gulf, launching Operations Earnest Will and Prime Chance against the Iranians.