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.

Sen. Tammy Duckworth, an ex-Army Black Hawk pilot, said communications between airline and military pilots usually go through air traffic control.

A gasp can be heard on air traffic control audio as an American Airlines plane and a US Army helicopter collided in Washington DC on Wednesday, 29 January. American Eagle flight 5342 – carrying 64 people – and the military Black Hawk helicopter – carrying three people – crashed at approximately 8:53 p.