A barrage balloon is a large uncrewed tethered kite balloon used to defend ground targets against aircraft attack, by raising aloft steel cables which pose a severe collision risk to aircraft, making the attacker's approach more difficult. The design of the kite balloon, having a shape and cable bridling which stabilise the balloon and reduce drag, meant that it could be operated with more wind than a circular balloon could. Some examples carried small explosive charges that would be pulled up against the aircraft to ensure its destruction. Barrage balloons are not practical against very high altitude flying aircraft, due to the weight of the long cable required.