The National Transportation Safety Board uncovered more than 15,000 “near-miss events” between helicopters and jets at Reagan National airport in just three years leading up to the American Airlines jet and Army helicopter collision that killed 67 people.

Over 15,000 close calls between planes and helicopters occurred in three years before the American Airlines and Black Hawk crash.

The National Transportation Safety Board has released their preliminary report into the deadly midair collision between an American Airlines flight and a U.S. Army Black Hawk helicopter over Washington,