Flying high over Baltimore last week, two Martin 404 airliners hurtled toward each other on what seemed like a sure collision course. Seconds before disaster, the planes suddenly veered apart. One swept upward; the other dipped slightly. So coolly had the maneuver been executed that it seemed as if an invisible electronic hand had guided the controls.
Both pilots, in fact, did have a helping hand. The "near miss" was the first public demonstration of a promising new collision-avoidance system (CAS) that may reduce some of the risks of flying in the nation's increasingly crowded skies. Last year the U.S....