US Transportation Secretary Sean Duffy said there was a "consolidation of air traffic controllers an hour before it was supposed to happen".

Officials are examining black boxes from both aircraft and say they appear to be in good condition and may provide details on what went wrong.

A recording obtained by this news organization contains chatter between airport tower employees and crew on the small plane before it went down.

A single controller was left to handle the air traffic of planes and helicopters flying over the airspace when two people would typically be monitoring both flight paths

There's still a lot we don't know and initial speculation from the media and the president about the causes of Wednesday's disaster appear off-base.

The National Transportation Safety Board has interviewed the air-traffic controller who was working at the time of the midair collision, board member Todd Inman said, adding that the interviews have been ongoing throughout the day.