On September 4, 2004, at approximately 1350 mountain daylight time, a Gates Learjet 25B, N47MR, operated by American Jets, Inc., was substantially damaged when both tires blew during the takeoff roll from City of Colorado Springs Municipal Airport (COS), Colorado Springs, Colorado. Visual meteorological conditions prevailed at the time of the accident. The lifeguard flight was being operated on an instrument flight rules flight plan, under the provisions of Title 14 CFR Part 135. The pilot, co-pilot, two crew members and a passenger reported no injuries. The cross-country flight was originating at the time of the accident and was en route to Memphis, Tennessee. According to the accident report submitted by the operator, during the takeoff roll, the airplane began to vibrate on the right side and then the right tire blew. The left tire blew shortly thereafter. In a statement made by the co-pilot, the "captain maintained directional control" and the drag chute was deployed. The airplane came to rest at the departure end of runway 17L. A postaccident investigation revealed that metal from the landing gear penetrated the wings and the fuselage was wrinkled. An examination of the airplane systems revealed no anomalies. The reason for the tire failure was not determined.