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.

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.