INTRODUCTION The ESDU Aircraft Performance Program is a suite of programs to predict the performance of an aircraft design for which appropriate aerodynamic and powerplant data are available. This suite consists of programs to predict@ ?Point and path performance (Flight Performance)@ ?Take-off and landing performance (Airfield Performance)@ ?Mission performance (Military: Radius of Action or Civil: Block Fuel or Block Time). Figure 1 shows a simple hierarchical block diagram of the main program modules and the ESDU Data Items that contain relevant equations@ techniques or assumptions. Figure 1 also shows how the modules in each program are inter-related. The highest level of modules are the control modules for the Airfield and Radius of Action/Block Fuel or Block Time programs. These control programs call the ??path performance' modules. Below these are the ??point performance' routines which are also used as service routines by the higher level path performance programs. Below these ??point performance' calculations are the ??general service routines'. The Flight Performance program is constructed using the ??path performance' and ??point performance' modules. There is provision for simple local searches for single-variable optimum conditions. The programs being issued in the first release are as follows. APP_01@ the Performance Program Pre-processor@ APP_02@ the Flight Performance Program@ APP_03@ the Interpolation Program.