When aircraft volume goes down, a supervisor can make the decision to combine two controller positions into one position. This happens routinely, and on Wednesday at Reagan Airport, it happened 40 minutes earlier than it normally does because the supervisor determined that the traffic was low enough to combine, according to a source with direct knowledge.

This position handles local arrivals into Reagan and helicopter traffic when it’s combined.

Reagan is not understaffed, the source added.

The air traffic controllers’ union said in a statement that it's working with all federal agencies and "stands with the highly trained, highly skilled" workforce that "keeps the United States as the gold standard for aviation safety."

-ABC News’ Sam Sweeney

Dive teams are ceasing operations on the Potomac River because they have recovered all of the bodies they’re able to without moving the fuselage, two sources familiar with the operation told ABC News.

About 40 bodies have been recovered so far, including at least one of the soldiers from the Army helicopter, the sources said.

Additional bodies and human remains will need to be extracted from the wreckage once it is lifted to the surface of the river.

Crews are bracing for the possibility that some of the victims will not be recovered because of the fireball that resulted from the collision, the sources said.

-ABC News’ Katherine Faulders and Aaron Katersky

Samuel Lilley, the first officer on board American Airlines Flight 5342, recently got engaged, his sister, Tiffany Gibson, told ABC News.

"He was an amazing person. He loved people. He loved adventure. He loved traveling. He was excited. He was young. He was so young, and he was excited about life and his future and getting a dog and a house and kids. And it's just, this is just tragic," she said.

Samuel Lilley’s former brother-in-law, Greg Gibson, remembered him for his passion for flying and willingness to help others.

Samuel Lilley died on the same flight path his father, Timothy Lilley, flew for years. Timothy Lilley flew Black Hawk helicopters for the Army, transporting passengers over the Potomac River from his base in Virginia.

“We were stationed in Virginia, and [Timothy Lilley] flew that same route back and forth to the Pentagon, over and over and over again until he retired,” Tiffany Gibson said.

-ABC News’ Peter Charalambous

National Transportation Safety Board investigators are on the scene of the crash and plan to have a preliminary report within 30 days, NTSB Board Member Todd Inman said.

Flight recorders have not yet been recovered but the NTSB is "comfortable and confident" that the recorders will be recovered, Inman said.

The NTSB does not know enough facts to rule in or out human or mechanical factors at this time, Inman said.

"Our investigative team will be on scene as long as it takes in order to obtain all of the perishable evidence and all the fact finding that is needed to bring us to a conclusion of probable cause," Inman said. "Our mission is to understand not just what happened, but why it happened, and to recommend changes to prevent it from happening again."

NTSB Chairwoman Jennifer Homendy added that they do have "substantial" information but do not want to share anything before it’s verified.