PETERSON AFB, Colorado, Oct. 23 -- The North American Aerospace Defense Command issued the following news release: North American Aerospace Defense Command (NORAD) will conduct a planned live-fly air defense exercise near Merced, California, today. NORAD F-15s and civilian aircraft will participate in the exercise. Aircraft will operate at approximately 7,500 feet, and will likely be visible to the public. NORAD routinely conducts air defense exercises using a variety of scenarios, including  more PR