My initial reaction to this is the fact that the co-pilot didn't attempt to seize the plane from the pilot or other crew, but only took advantage of an opportun

My initial reaction to this is the fact that the co-pilot didn't attempt to seize the plane from the pilot or other crew, but only took advantage of an opportunity. In this specific case, it may be possible that the co-pilot would not have forced the situation where he was in sole control of the plane. The emotional side of me wants to call the man a coward, and a coward wouldn't be openly aggressive towards a flight attendant, but that's not a very productive point of view. In future cases, there's just no reason why a future murderous co-pilot couldn't be more aggressive, so it's still a situation worth considering.