During the 90-day Space Technology 5 (ST-5) mission, a total of 2535 auroral field-aligned current (FAC) signatures were identified. Of these 1030 were suitable to be modeled as semi-infinite current sheets aligned with L-shells and moving with constant speed in the north or south directions (hereafter called FAC speed). FAC speeds were found to range from −1 to 1 km/s with larger mean magnitude during intervals of higher geomagnetic activity. At ST-5 altitudes, ∼300 to 4500 km, the median relative errors in FAC thickness and current density, when stationary FAC is assumed, are 4%. When the ST-5 FAC speed determinations are extrapolated along the IGRF-10 magnetic field lines, these errors increase to 23% and 24% at 4 RE, and 65% and 124% at 8 RE, respectively.