I met Mason (Chickenhawk author) a few years ago, believe it or not, wandering around a helicopter museum. At a loss for words (for probably the only time in my life) and not wanting to ask the same questions that I'm sure every other reader asked I told him that I found the ending really surprising.
His response: "So did I".
Just proving that you can't imagine what it would be like flying in those conditions unless you've been there.
I first read the book as a brand new Twin Huey co-pilot flying in Haiti - quite an eye opener for a new pilot far from home. I think I'll start reading it again tonight!