The three main objectives of this research were to identify the actual reasons for schedule problems across large Air Force system development efforts, to quantity the importance of each category of reasons in terms of frequency and severity, and to demonstrate that the reasons for schedule problems are not program unique, but are common across system development efforts. To this end, this thesis contains a categorization and analysis of 549 reasons for schedule difficulties on 22 large Air Force Engineering and Manufacturing Development (EMD) programs from 1981 to 1994. These aircraft, missile, aircraft equipment, aircraft upgrade, and simulator programs had contract values ranging from 40Mtoover10B. All reasons were extracted from narrative explanations of negative schedule variances contained in contractor generated Cost Performance Reports (CPRs). Reasons for schedule problems were placed into categories, and categories were ranked by frequency of problems, total schedule variance (in dollars), and total schedule variance (in work days). Seven categories (technical problems, late subcontractors, manufacturing problems, design changes, late data, contracting, and staffing) accounted for 49 percent of the frequency, 57 percent of the schedule variance (in dollars), and 49 percent of the schedule variance (in work days)
