One thing that irks me in the Arrow season finale is the massive continuity error regarding the incoming nuclear warhead to Star City. Felicity could see it coming and have enough time to program it to change course.
Nuclear warheads travel at supersonic speeds. The warhead would strike Star City in the blink of an eye, even if Felicity could see it. Can she see something so tiny in the sky?
Nuclear warheads are ballistic. That means they don’t fly under their own power (and they don’t leave a smoke trail in the sky) and there’s no way to electronically get them to change course.
The show’s writers were either too lazy or too stupid to write a proper ending to the story. They couldn’t be bothered to do a modicum of research to understand exactly what they were writing. Utterly astonishing in this day and age.