Just offshore of the towering national monuments of Washington, a tall crane now hovers over the Potomac River. It casts a large shadow over the effort to understand what caused the collision of a passenger jet and a military helicopter last Wednesday as a new phase of the recovery starts.

Crews are on the scene on the Potomac River to retrieve the submerged wreckage of an airliner and an Army helicopter that collided midair in the deadliest U.S. air disaster since 2001.

Crews using a crane lifted the first pieces of wreckage from the downed American Airlines regional jet from the Potomac River on Monday morning as rescue workers sought to recover all 67 bodies from the crash site near Ronald Reagan National Airport.