'releases' and 'drops'—until the complete system had been delivered. Sea trials of Collins were unable to commence until Release 1.5 of the combat system software was delivered; because of ongoing delays in the provision of the software, the early phases of the trials were completed using stand-alone equipment By March 1994, the combat system had become the major area of concern for the submarine project: assembly of the system was almost nine months behind schedule, and at least 20% of the software had not been compiled. The combat system continued to be a problem during the next few years, with progressive drops offering little improvements in performance over the previous version, and the completion date of Release 2—the designation for the full contractual realisation of the combat system software—was continually postponed. In 1996, Rockwell sold its military and aerospace division, including responsibility for the Collins combat system, to Boeing. Boeing attempted to produce a workable combat system, but believed that this could only be done if the changes in technology were accounted for in a contract alteration, which the RAN and the Australian Government initially refused to do. Boeing then requested assistance from Raytheon, and after further negotiations with the Government resulted in a reduction of the system capabilities, the companies were able to stabilise the system and deliver Release 2.0 at the end of 1999. Boeing sold its naval systems division to Raytheon in May 2000, making the latter company solely responsible for completion of the combat system. After this, the submarine project began investigating ideas for a new combat system. Because there was not enough time to evaluate the replacement system to include it in the "fast track" program, Dechaineux and Sheean were fitted with the old Rockwell combat system, which was enhanced by the addition of sub-systems developed during the early 1980s for the Oberon-class mid-life upgrade and commercial off-the-shelf components. Even with the enhanced system, it was believed that the capabilities of the fast track Collins boats was at best equivalent to the Oberons. Lockheed Martin, Thales, STN Atlas, and Raytheon were approached to provide tenders to design and assemble a new combat system for the submarines, with all four submitting proposals during early 2000. In May 2000, after the DSTO tested operational versions of the proposed combat software packages, the Lockheed and Thales tenders were eliminated, despite the Thales proposal being rated better than Raytheon's.