Lawmakers have expressed concerns about congestion in at Ronald Reagan Washington National Airport amid a constricted space.

"More and more planes on this busiest runway in the United States is just going to increase the chance of a significant incident," Sen. Tim Kaine warned a year ago.

The airspace around Ronald Reagan Washington National Airport has long been problematic due to heavy military and commercial flight activity in the nation’s capital, according to industry insiders.

At least one aircraft crashed Wednesday evening over the Potomac River near Ronald Reagan International Airport outside Washington, D.C., officials said, grounding all flights at the airport. The District of Columbia Fire and Emergency Medical Services Department reported in a social media post that a small aircraft crashed in the Potomac River in the "vicinity" of the airport.

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