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.

Wreckage of the military helicopter involved in a mid-air collision with an American Airlines passenger jet that killed all 67 people on both aircraft was recovered from the Potomac River, federal officials said.