ALOFT-FTTM (A Large Outdoor Fire plume Trajectory model - Flat Terrain) is a computer based model to predict the downwind distribution of smoke particulate and combustion products from large outdoor fires. Measurements and observations at experimental fires have shown that the downwind distribution of smoke is a complex function of the fire parameters, meteorological conditions and topographic features. To incorporate these features, NIST has developed a smoke plume trajectory model that solves the fundamental fluid dynamic equations for the smoke plume and its surroundings. ALOFT-FT is the public domain version of the model for flat terrain using windows based personal computers. The program contains a graphical user interface for input and output and a user modifiable database of fuel and smoke emission parameters. The output can be displayed as downwind, crosswind and vertical smoke concentration contours. Information on using the program is available with on-line help commands in the program.