 During the Atlantic U-boat campaign of World War I, kite balloons would be deployed by a destroyer escorting a convoy of merchant ships.A basket suspended below the kite balloon held a pilot who watched for U-boats and notified the destroyer of his observations by telephone via the insulated core of the kite balloon tether cable.The elevated balloon pilot had a clearer view of a submerged U-boat than was available from shipboard locations; and the kite balloon pilot could notify the ship of the U-boat's evasive maneuvers during a depth charge attack.