ACM is a LAN-oriented, multiplayer aerial combat simulation. My main design objective was to provide source code that could be easily compiled and executed on a wide variety of platforms. To that end, acm is written entirely in C, exploiting the programming features of Unix, X11, and the BSD socket interface. Players engage in air to air combat against one another using heat seeking missiles and cannons. ACM is implemented as two programs. The first, named "acm", is a small program that, when invoked, starts a flight session on a given workstation. The second component, named "acms", is a server process that manages the multiplayer environment. It also manages the flight simulation and display management that is required. Most players will prefer to run the acms process on a back-end server system on their local area network. Players at client workstations can then invoke the acm program to begin play.