Washington DC plane crash: What led to the worst US air disaster in 25 years that led to death of 67 people?

The Black Hawk helicopter involved in the fatal mid-air collision with American Airlines plane near Ronald Reagan Washington National Airport was reportedly flying higher than permitted and outside its designated flight path. According to several sources, the helicopter was expected to operate at a lower altitude and in a different location within the airspace.
 

This revelation raises concerns about the events leading up to the collision. The air traffic control tower at Reagan National Airport was also understaffed at the time of the incident, with one controller handling both helicopter traffic and arriving/departing planes.

Typically, these duties are divided between two people, but the airport often combines the roles after 9:30 pm when traffic slows down. However, on the evening of the collision, the roles were combined earlier as directed by the tower supervisor.
 

Despite the staffing issues, a person familiar with the matter claimed that the tower staffing was at a normal level. Additionally, a top Army aviation official stated that the helicopter crew was "very experienced" and familiar with the congested flying conditions in the area. The crew had even flown the specific route before, at night.

An investigation has been launched, with the National Transportation Safety Board (NTSB), the Federal Aviation Administration (FAA), and the US Department of Defense all involved. The investigation will likely examine the factors contributing to the collision, including the helicopter's flight path and the air traffic control tower's staffing.