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

A retired Army helicopter pilot shared insights into what may have caused Wednesday’s deadly mid-air collision over the Potomac River in Washington, DC.

While driving home, Ari Shulman said a "spray of sparks" in the sky caught his attention as he watched in horror the midair collision unfold.

Emergency crews responded to a fatal aircraft collision involving an American Airlines passenger jet and Black Hawk helicopter over the Potomac River.

Officials say the conditions of the Potomac River complicated recovery efforts of the bodies those killed in a mid-air collision between American Airlines flight 5342 from Wichita and an Army

A passenger jet and a Black Hawk helicopter collided in midair Wednesday and crashed into the Potomac River near Reagan National Airport near Washington, D.C., officials said.

A Georgia high school says that one of the soldiers involved in the mid-air collision was a former student and a member of their MCJROTC program.

A PSA Airlines Bombardier CRJ700 regional jet carrying several dozen people collided with an Army Black Hawk helicopter. Reagan National Airport has grounded all flights.

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.

A PSA Airlines Bombardier CRJ700 regional jet collided with a Black Hawk helicopter while on approach at Reagan Washington National Airport at about 9 p.m. Wednesday.

All are feared dead in a crash involving a Black Hawk helicopter built by Connecticut's Sikorsky and an American Airlines plane in Washington, D.C.