That in the scene before King's Landing when Cersei executes Messandri of Naath, Cersei could have had 4 or 5 of the scorpions on Drogon (who was in the background, but in range) and then saved a few for Danny and co.
They were standing right there. I find it hard to believe that Cersei would have respected the white flag of parley that much. She nuked the Great Sept of Bailor without missing a beat. She could have eliminated the senior leadership of her enemy in one go....
~Jeordam
Saving the Princess, Humanity, or the World-Entire since 1985