(In the books the only way to kill a mature dragon while flying was a shot through the eye. Nothing else would do enough harm. You could knock them out of the sky via a shot in the wing, but their scales were way too hard for a bolt to pierce it.)
Building on what I posted earlier, the show has been severely damaged by two things: A) Euron's storyline changes amd B) The lack of Aegon Blackfyre.
Aegon- Young Griff- is possibly the son of Rhaegr Targaryen and Elia Martell. Which would make him Jon's half-brother. The books make it clear something else is going on and he's likely in fact a Blackfyre (bastard Targaryen), but the people believe him to be the son of Rhaegr, which is what gives him power. Plus he's young and charismatic. In the books, Aegon has already raised his banners and has taken Dorne, Stormwind, and the Reach. What this means is that Cersei has a legitimate threat besides Dany, and Dany isn't just going to waltz north and take out the city and Cersei easily, so we don't have to have stupid decisions like the dragon being killed to make Cersei a threat to Dany, because there is a major third player that is missing- to whom, I might add, every indication is that Varys is secretly supporting.
Euron Crows-Eye's story goes beyond even what I posted earlier. He is almost certainly working with the Others or attempting to use them. It is heavily implied that the Three-Eyed Raven tried to make him his apprentice and failed miserably, as Euron still sees visions. He ties up priests of all religions on his ship, the Silence, (so named because he cut out the tongues of everyone under him so they cannot speak as to what they see) and gives them a drink that the Ironborn use to come close to death and thus they see visions. He has a horn from the ruins of Valyria that supposedly can turn dragons to fight for him, he uses blood magic to control the weather and he has an entire suit of armor made out of Valyrian steel. He is simply a genuine huge threat that doesn't give a fuck about the Game of Thrones, he thinks he is the Drowned God in the flesh, and his goal is to conquer the entire world and turn himself into a god.
I get we had to cut things, but Aegon missing from the show takes out what should be a major third player in the War for the Iron Throne. Euron could possibly be the big baddie in the books, or at least working with the big baddie. In the show he's just a Saturday Morning Cartoon villain.
Also: The Winds of Winter is done according to rumor. Rumor also has it a Dream of Spring is ALSO done, he's simply waiting for the show to finish and giving it time. And GRRM has come out and said the show has entirely diverged from the books.