WASHINGTON (NewsNation) — The collision Wednesday night between a military helicopter and American Airlines Flight 5342 happened in some of the world’s most tightly controlled airspace, just over 3 miles south of the White House and the U.S. Capitol.

The collision happened at around 9 p.m. when a regional jet at the end of a flight from Wichita, Kansas, collided with a military helicopter on a training exercise, according to the Federal Aviation Administration.

The helicopter was a UH-60 Black Hawk based at Fort Belvoir in Virginia flying south over the Potomac River as the American Airlines flight was flying north.

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.

Less than 30 seconds before the collision, an air traffic controller asked a helicopter if it had the arriving plane in sight. The controller made another radio call to the helicopter moments later, saying, “PAT 25 pass behind the CRJ” — apparently telling the copter to wait for the Bombardier CRJ-701 twin-engine jet to pass. There was no reply. Seconds after that, the aircraft collided.

The plane’s radio transponder stopped transmitting about 2,400 feet short of the runway, roughly over the middle of the Potomac River.

The body of the plane was found upside-down in three sections in waist-deep water, officials said. The helicopter’s wreckage was also found.

The Associated Press contributed to this report.