Near the end of Our Kind of Traitor, the helicopter descends out-of-control then explodes, killing Dima, and others. It was not obvious to me how this happened. Was it the Mafia earlier on? Was it Dima himself, to save his family?
I think Dima did it himself in order to protect his family. Once he was out of the way the bad guys would have no more reason to go after the family and he had planned ahead to leave the gun with his wife, containing the secret information Hector needed. He planned the whole thing. The proof to me was when he told Perry not to come on the helicopter and poor Luke and the pilot got caught up in it.