Alarmed by a spate of near-collisions involving airliners, the government is trying to find out why air traffic controllers and pilots are making so many dangerous errors. In recent months, there have been at least a half-dozen incidents in which airliners came close to colliding with other planes or helicopters — including in Chicago, Houston, San Francisco, Burbank, Calif., and Anchorage, Alaska. In some cases, pilots made last-second changes in direction after cockpit alarms went off warning of an impending crash. "This spring we had several close calls that got everybody's attention, and I think that's the thing that really...
