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.

After American Airlines Flight 5342 and a U.S. Army helicopter collided mid-air, officials shared insight into the respective pilots’ communication with air traffic control.

Readings have been compared from the black box recovered from American Eagle flight 5342 and the air traffic control tower about the Black Hawk helicopter