In shots of the school bus going down a hill out of control, there are no children aboard. When Superman finally brings the bus to a stop the children are on board.
In the closing fight scene, Superman gets hit over the head and is covered with powdery chunks of debris. But in the next closeup, his hair is immaculately slick and groomed without a speck of debris in it.
In the plane, Kent punches Hadley to knock him out so he can turn into Superman. Later, Hadley asks Kent how he was blacked out but managed to land the plane safely. As far as Hadley knew, Kent was still in the plane with him and could have landed it, even though Superman actually did.
In the closing fight scene, it is obvious that a stunt man is substituting for George Reeves.
After Superman breaks into Crannix's hideout, Crannix fires his gun at him. He is clearly shooting to the left and not directly at Superman.
Three hoodlums break into the scientists office and kidnap the professor and the mind machine, but when the other scientist looks out the window to see them driving away, there are only three men in the convertible.
There is a video screen on the Mind Machine that can show images from the Hearing Committee room, but there is no camera in the room to produce the images.
After Superman saves the school bus and is flying you can plainly see a repair to his suit under his left arm using black thread.