Jets commonly use a micro-turbine or ducted fan to power them. Most airframes are constructed from fiberglass and carbon fiber. For electric powered flight which are usually powered by electric ducted fans, may be made of styrofoam. Inside the aircraft, wooden spars reinforce the body to make a rigid airframe. They also have Kevlar fuel tanks for the Jet A fuel that they run on. Most micro turbines start with propane and burn for a few seconds before introducing the jet fuel by solenoid. These aircraft can often reach speeds over 320 km/h (200 mph).