the flight takes off from teterboro, new jersey, and is headed to ocean city, new jersey. >> in this case, the direction of flight was going to take this piper right over the hudson river as it transited through the new york city skyline area. >> two minutes later, at 11:52, the helicopter, facing west, lifts off, climbing straight up, then proceeds south. because the hudson river is part of new york's visual flight rule corridor, neither pilot has filed a fight plan. >> both were operating under visual rules, which is a scene avoid rule. like you drive your car, you seek conflicting traffic. it's same thing with airplanes. >> the flight following is if the air traffic controller is not too busy with instrument traffic, they can radar identify an airplane and provide traffic advisories to the pilot. >> by 11:53, the helicopter is at 900 feet and climbing, still heading south. the piper, cruising at 1100 feet, has reached the hudson and is now only yards from the helicopter. the weather is good. visibility is ten miles with no clouds obscuring the aircraft. so why didn't they see and