(The RAAF only acquired air-to-air refueling for the F/A-18, possibly to avoid causing difficulties with other Asian countries by increasing the F-111C's already great range.) Training began in 1967, with RAAF personnel seeing terrain-following radar and other sophisticated equipment for the first time. However, development delays and structural problems delayed acceptance of aircraft by the RAAF until 1973. These issues were mainly to do with the wing attach points, and the redesign of the F-111 engine intakes. Completion of contractual requirements to the satisfaction of Australia also took time, damaging the morale of the hundreds of trained RAAF personnel who had little to do. The program costs, during 1963–1967, grew at an alarming rate; estimates by the USAF at the start of the program was placed at US$124.5 million, but by April 1967 had risen to $237.75 million. While the initial price of US$5.21 million per aircraft was capped at US$5.95 million, R&D, labor, and other costs were not. The rising price, three unexplained losses of USAF F-111As in Vietnam during their first month of deployment, and the British and U.S. Navy's orders' cancellations caused further controversy in Australia during 1968. By 1973, however, when the F-111A had accumulated 250,000 flight hours, it had the best safety record among contemporary aircraft, which presaged the F-111C's own excellent record. Four aircraft were modified to RF-111C reconnaissance configuration during 1979–80, retaining their strike capability. The RF-111C carried a reconnaissance pack with four cameras and an infrared linescanner unit. Four ex-USAF F-111As were refitted to F-111C standard and delivered to Australia as attrition replacements in 1982. There F-111Cs were equipped to carry Pave Tack FLIR/laser pods in the mid-1980s. They underwent an extensive Avionics Upgrade Program through 1998. Under this program, the F-111C was upgraded to digital avionics. This included twin mission computers, modern digital databus, digital weapon management system, new AN/APQ-171 terrain-following radar, new AN/APQ-169 attack radar, and twin ring-laser gyro INS. In late 2001, wing fatigue problems were discovered in one of the F-111C fleet. As a result, a decision was made in May 2002 to replace the wings with spares taken from ex-USAF F-111Fs stored at the Aerospace Maintenance and Regeneration Center (AMARC).