Safety investigators probing January’s midair collision between an American Airlines Group Inc. regional jet and a US Army Black Hawk near Washington found a key instrument on the helicopter was displaying inaccurate altitude data that could have led the pilots to think they were flying lower than they actually were.

Investigators conclude pilots of Black Hawk did not hear warning from air traffic controllers to pass behind jet

The pilots of a Black Hawk helicopter that collided with a passenger jet near Washington Reagan National Airport in January likely didn't know how high they were flying or how close they were to an airliner before the deadly crash,

Three days of investigative hearings on the deadly midair collision between a military helicopter and passenger plane over Washington begin Wednesday morning and may reveal new insights into the crash