Technically it's a documentary, but the producers skillfully wove it into the form of an action movie with a rising intensity to a gripping climax that is much more intense because you are watching life-and-death reality, not something pretend. As such it starts out "normal" but packs a huge emotional punch by the end.
One movie I didn’t see mentioned (but maybe it was there) I thought was great in it’s time was “GIANT” made in ‘56. So many really good movies were mentioned that it would be hard to pick a favorite.