Revealing mistake: After Superman is thrown into a building, it cuts to Jimmy and Lois strapping themselves into a helicopter. The seatbelts in the chopper are not drawn correctly. The holes where they come out of the seat are not symmetrical, don't match from one seat to the next, and are overlapping the edges of the fabric on some and not on others. And then when it cuts to a side view of Lois, the holes are gone and it looks like the belt just stops at the seat.
Picture added by Quantom X