An Army Black Hawk helicopter collided with a regional jet near Ronald Reagan Washington National Airport on Wednesday evening, U.S. officials confirmed to ABC News.

This data point is one of several key mysteries investigators are exploring as they seek to explain what caused the nation's worst air disaster in more than a decade, aviation experts said.

Here's what is known about the Black Hawk and its crew that crashed into the American Airlines passenger jet over the Potomac River in Washington.

Wednesday’s fatal collision and two other incidents dramatically illustrate the challenges pilots and air traffic controllers ...

Retired U.S. Army Col. Larry Connell knows the kinds of challenges that pilots of Black Hawk helicopters can face. He told Target 12 he was shocked to learn a crew flying had collided with a regional ...

Investigators will be looking at everything from air traffic communications to technology failures that may have contributed ...

A look at the victims of Wednesday’s devastating mid-air collision between an American Airlines jet and a U.S. Army ...

The service is often responsible for ferrying lawmakers and other V.I.P.’s across the area, and near Reagan National Airport.