There were 64 passengers aboard the plane, and three Army soldiers in the helicopter, according to officials. Here's a look at what we know about the victims.

An American Airlines regional jet went down in the Potomac River near Ronald Reagan Washington National Airport.

An American Airlines plane carrying 60 passengers and four crew members collided with an Army Black Hawk helicopter outside Reagan National Airport near Washington, D.C. Wednesday evening. Three soldiers were onboard the helicopter and a massive search and rescue operation is now unfolding in the Potomac River.

The Post can reveal that miscommunications in one of the most crowded and complex patches of sky in the US are likely to blame.

A few minutes before the jet was to land, air traffic controllers asked American Airlines Flight 5342 if it could do so on a shorter runway, and the pilots agreed. Controllers cleared the jet to land, and flight tracking sites showed the plane adjust its approach to the new runway.

Ryan O’Hara, a father-of-one, was one of the three soldiers aboard the military helicopter, according to reports

The Army Black Hawk helicopter that collided with an American Airlines commuter plane near Reagan Washington National Airport in Virginia Wednesday was on a “training flight” when it crashed into the Potomac River, according to the military service branch.

Video recorded by bystanders shows the harrowing moment when the 2 aircraft crashed into one another, causing an explosion over the nation's capital.

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.

The Army official said that the pilots were on a routine training flight along a familiar flight path that isn't particularly complicated.

The Black Hawk is a US Army workhorse helicopter. It has been flying for decades. One tragically collided with a passenger jet this week.