Diving crews are still searching the icy waters of the Potomac River looking to retrieve the bodies of all the people killed in this week’s plane and helicopter collision. Retired Black Hawk instructor pilot Martin Gottholm discusses the difficulties in flying at night for Black Hawk pilots and questions surrounding the altitudes of the aircrafts at the time.

The incident comes a week after an American Eagle regional jet collided with an Army Black Hawk helicopter over the Potomac River near Washington D.C. The reasons as to why the plane was interrupted in its journeys over the past month is unknown

As to what may have gone wrong and caused an American Airlines commercial jet and a military helicopter to collide, we spoke with a former NTSB investigator and former Black Hawk helicopter pilot to weigh in on the subject.

Data from a cockpit voice recorder of the Black Hawk helicopter that collided with an airliner near Washington, D.C, last week suggests the crew was wearing night-vision goggles.