U.S. authorities said on Thursday it was not yet clear why a regional jet crashed into a U.S. Army helicopter at a Washington airport, killing 67 people in the deadliest U.S. air disaster in more than 20 years.

An Army helicopter on a training flight collided with an American Airlines regional jet that was on approach into Washington D.C.'s Reagan National Airport.

President Donald Trump began his White House briefing Thursday with a moment of silence and a prayer for victims of Wednesday's crash at Reagan National Airport. Trump on Thursday variously pointed the finger at the helicopter’s pilot,

Wednesday night’s crash of an American Airlines commuter plane in Washington is one of the worst disasters for the Fort Worth-based airline in more than two decades.