If changes aren't made, that near-miss becomes a mid-air collision,” one aviation safety expert said. “Unfortunately, that's what we had last night.”

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.

A day after the United States witnessed its deadliest aviation disaster in over two decades, a preliminary report from the Federal Aviation Administration (FAA) suggests the Reagan National Airport control tower — responsible for guiding pilots—was understaffed,