On August 8, 1995, at 0710 mountain daylight time, an Aerostar S- 81-A (hot air balloon), N9174Z, registered to and operated by Black Hills Balloons of Custer, South Dakota, was substantially damaged during a hard landing one and one-half miles north of Custer, South Dakota. The pilot and five passengers reported minor injuries. Two passengers sustained serious injuries. The 14 CFR Part 91 sightseeing hot air balloon was operating in visual meteorological conditions. No flight plan was on file. The flight departed from an open field near Custer, South Dakota, at 0615. The pilot stated, "Upon landing an incredible gust of wind picked the balloon up and carried it across the road into some pine trees." A weather special observation taken 25 miles to the northeast of the accident site at 0737, contained in the remarks section the notation that there was a windshift at 0734 with frontal passage. The previous surface observation at 0650 reported wind as 120 degrees at 6 knots; whereas the special observation at 0737 reported wind as 010 degrees at 13 knots.