I think Brian will survive because he has the basic necessities and skills to survive like a hatchet. Pilots also have been trained to have the knowledge of surviving remote locations. You could also argue that Brian has his world shaken by a divorce that will break his mental health but I think Brian would stay sane in that situation cause it’s life or death. He can just hunt for food using a swift blow of his hatchet but if he doesn’t find any animals he can try and find fruit. If not then he won’t survive. So it’s a real stretch if he can pull himself together he survives if he has a mental breakdown then he is dead.
Now on to my second point Brian can also build a shelter to protect him from rain hail etc if the shelter breaks he can rebuild it using some wood he gathered. He can also build some equipment like a hammer. If you argue that he will freeze to death then objection buddy he can make a fire using wood because as I mentioned earlier pilots are trained to survive in the wild. He can also use equipment from the crashed plane like a flare gun and he can make some signals using sticks or leaves of the trees. If you argue that he will dehydrate there is a method of purifying water if he doesn’t know he can just drink his urine because urine is clean. He can hunt for his food since the wild has many animals such as deer boar and birds. He can also purify rain water using certain methods.