*.FSM

The FreeSpace 1 mission file format. Almost identical to *.FS2 mission files used by FreeSpace 2, although the FS2 format has several additional features as well as some minor differences in syntax. .FSM files can be loaded by FreeSpace 2, although .FS2 files cannot be loaded by FreeSpace 1. (Given that ship classes, briefing icons, head animations, and other nuances were updated or tweaked in FreeSpace 2, however, it is advisable to use the Import Mission feature in FRED2_Open rather than opening a .FSM file directly.)