Investigators trying to determine what caused last week’s deadly midair collision between a US military Black Hawk helicopter and an American Airlines plane near Washington, DC, briefed lawmakers Thursday on what they’ve learned after combing through data from both aircraft and air traffic control.

The Army Black Hawk helicopter that collided with an American Airlines commuter plane near Reagan Washington National Airport in Virginia Wednesday was on a “training flight” when they crashed into the Potomac River, according to the military service branch.

The Federal Aviation Administration and National Transportation Safety Board plan to brief senators Thursday on last week's midair collision between an American Airlines passenger jet and a military helicopter near Washington's Ronald Reagan National Airport that killed 67,