In this report, we examine Cost Adjustment Sheets (CASs) that modify the Navy s Flying Hour Program (FHP) budget to assess whether process reforms may be appropriate. CASs modify the FHP baseline budget of a Type Model Series (T/M/S). There are two ways in which a T/M/S baseline budget is formulated: For a newer aircraft lacking representative historical data, the T/M/S managers develop a budget more than a year in advance of the budgetary execution year based on expert insight and judgment including experiences with analogous aircraft. For older aircraft, prior annual costs (or expenditures) per flying hour (CPH) serve as the foundation of the baseline budget. After formulation of each T/M/S baseline budget but before commencement of the year of budgetary execution program managers, Integrated Weapons System Team leads, and fleet class desk representatives are responsible for researching relevant aircraft support issues and, if necessary, developing CASs that modify what then becomes the execution budget (XB), the last budget formulated before a fiscal year commences. CAS usage varies considerably across T/M/Ss. The F/A-18 makes much greater proportional use of CASs than other T/M/Ss, relative to its share of the Navy aviation budget or Navy aviation expenditures. Use of CASs may not suggest anything unusual about a T/M/S cost structure or growth as much as it suggests delays in ascertaining a change to the T/M/S CPH. CASs can be submitted to reflect initiatives that are projected to reduce costs; they are also submitted to reflect modifications to in-service aircraft that are expected to incur operating and support costs, as well as transitions from one source of repair (such as interim contractor support) to another source (such as organic repair). The report has three major sections. First, we discuss CASs and how the Navy aviation community uses them. Second, we note the sometimes considerable differences between Navy aviation budgets (which are affected by CASs) and Navy aviation expenditures. Third, we examine expenditure-per-flying-hour growth across different Navy aircraft. We find that while the F/A-18 program makes much more use of the CAS process thatn other Navyh aircraft, there has been nothing unusual about its expenditure=per-flying-hour growth.