Carrie Underwood is mourning the death of her frequent collaborator Brett James after he died in a plane crash at the age of 57. "Some things are just unfathomable. The loss of Brett James to his family, friends and our music community is too great to put into words," Underwood, 42, wrote via her Instagram on Friday, September 19. "Brett was the epitome of 'cool.' I see him in my mind riding up to my cabins to write on his motorcycle [and] his hair somehow perfectly coiffed despite being under a helmet for however long.