There's an "intolerable risk to aviation safety" with helicopters and planes flying too close to each other near DCA.

Six weeks after 67 people perished in a D.C. midair collision, the NTSB’s preliminary report exposes a history of near misses between commercial jets and helicopters at the airport.

The transportation secretary’s decision came after the National Transportation Safety Board cited a long history of near collisions between helicopters and airplanes near the nation’s capital.