Across the continent from Newfoundland to Alaska the Canadian government is building an aerial military “highway,” a chain of radio beacons 250 miles apart to guide bombers or fighters or interceptor planes crossing America in an emergency. The project is a part of the joint defense plan of the United States and Canada. Besides serving the functions of the radio beacons that guide commercial planes throughout the states, these transmitting stations will form a patrol line from which air raid warnings can be flashed to bases farther south. Each beacon tower has special protection against sabotage and insulation that will maintain signal strength at constant power regardless of weather.