![Atc](http://rack.0.mshcdn.com/media/ZgkyMDE1LzA4LzEwLzEzL2F0Yy5lZWMwOC5qcGcKcAl0aHVtYgk1NzV4MzIzIwplCWpwZw/120bbe6d/b7d/atc.jpg)
WASHINGTON — Air traffic controllers' work schedules often lead to chronic fatigue, making them less alert and endangering the safety of the national air traffic system, according to a study the government has kept secret for nearly four years.
Federal Aviation Administration officials have...