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.

U.S. authorities said on Thursday it was not yet clear why a regional jet and a U.S. Army helicopter collided at a Washington airport, killing 67 people in the deadliest U.S. air disaster in more than 20 years.

DCA Ronald Reagan Washington National Airport has shut down and The Federal Aviation Authority has confirmed a American Airlines Flight operated by PSA Airlines collided mid-air with a Blackhawk Sikor

A jet carrying 60 passengers and four crew members collided Wednesday with an Army helicopter while landing at Ronald Reagan National Airport near Washington

Political leaders had warned about the dangers of Ronald Reagan Washington National Airport in Washington, D.C. months before an American Airlines flight collided with a U.S. Army Black Hawk helicopter on its approach to the airport.

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.”