The C-17 measures 174 feet long (53 meters) with a wingspan of 169 feet, 10 inches (51.75 meters). The aircraft is powered by four Pratt & Whitney F117-PW-100 turbofan engines, which are based on the commercial Pratt and Whitney PW2040 used on the Boeing 757. Each engine is rated at 40,440 pounds of thrust and includes thrust reversers that direct the flow of air upward and forward to avoid ingestion of dust and debris. Additionally, thrust reversers provide enough thrust to reverse the aircraft while taxing backwards and create in-flight drag for maximum rate descents. The design characteristics give it the capability to operate into and out of short runways and austere airfields carrying large payloads. Maximum use has been made of commercial off-the-shelf equipment, including Air Force-standardized avionics.