to retain the Sea Venoms and Gannets in service until at least 1967. Minister for Defence Senator Shane Paltridge rejected a proposal from the Navy to purchase an Essex-class aircraft carrier from the United States Navy in June 1964, and the next month Melbourne undertook flight trials with Douglas A-4 Skyhawk fighters and Grumman S-2 Tracker anti-submarine aircraft during a visit to U.S. Naval Base Subic Bay in the Philippines. American Trackers had previously operated from Melbourne in 1957 and several other occasions. The July 1964 trials proved that Melbourne could safely operate both types without the need for major modifications. In November 1964 Cabinet considered a proposal to modernise Melbourne and purchase 18 Skyhawks and 16 Trackers. It decided against acquiring Skyhawks, but agreed to the remainder of the project. Following further lobbying and staff work by the Navy, the Government eventually agreed to also purchase ten A-4G Skyhawks in early 1965. The cost of the Tracker acquisition was $A16.4 million. The Tracker order comprised 14 of the S-2E model, which were intended for operational service, and two former US Navy S-2A variants which were to be used as non-flying training aids and instructional airframes. The S-2E Tracker was a twin-engined aircraft with a crew of four. It could be armed with two homing torpedoes, two depth bombs or four depth charges within its weapons bay. 250 lb bombs or Mk 32 Zuni rockets could be mounted on its wings. The aircraft had a maximum range of and could stay aloft for up to nine hours. Its sensors included a AN/APS 39 radar and a magnetic anomaly detector, which extended from the belly and tail of the aircraft respectively. They could also carry sonobuoys to track submarines. Trackers had first entered service with the US Navy in 1954, and 1,285 were eventually produced. Preparations RAN personnel were trained to operate Trackers in North America during 1966 and 1967. The first RAN pilots to quality on the type were trained in Canada. Other pilots received training on the type at a US Navy facility at Corpus Christi, Texas. A detachment of maintenance personnel began a training program in the United States during mid-1966 and completed it late the next year. The RAN decided to use a different flight-deck crew composition for its Trackers than the US Navy and Royal Canadian Navy. Both of these navies crewed their Trackers with a