An air traffic controller at Reagan National Airport reportedly left early on Wednesday before the deadly collision between an American Airlines flight and a military helicopter.

The tragic, midair collision in Washington, D.C. is putting a spotlight on air traffic controller shortages. It's a nationwide problem, but the area around NYC is especially hard hit.

The NTSB is investigating "thousands of data points" to find the cause of the fatal D.C. plane-helicopter crash, including whether air traffic control staff was short personnel.