The probability of a bird strike in that area at that time was deemed to be low, according to the NTSB report.

During his military service - which included 20 years in the Ukrainian army - he served in Afghanistan and other ... including rescuing victims of a plane crash in Somalia in 2015.

Investigators previously said the helicopter may have had inaccurate altitude readings in the moments before the crash, and the crew may not have heard key instructions from air traffic controllers.