In Percy Jackson and The Titan's Curse, how can Percy fly?

Question

Having listened to most of the audio book of Percy Jackson and The Titan's Curse, I just realised something... How can Percy fly on Blackjack the pegasus without being struck down by Zeus who previously told Percy to stay out of his sky? Did I miss or forget a scene where the two settle their differences?

Answer 1

It is indeed very dangerous for Percy to fly

The danger in taking a plane is that Percy would be in the domain of Zeus, who has dominion over the sky. Due to how much Zeus dislikes Poseidon, Percy would be in serious danger:

“Oh,” I said. “Naturally. So we just get on a plane-”

“No!” Grover shrieked. “Percy, what are you thinking? Have you ever been on a plane in your life?”

I shook my head, feeling embarrassed. My mom had never taken me anywhere by plane. She’d always said we didn’t have the money. Besides, her parents had died in a plane crash.

“Percy, think,” Chiron said. “You are the son of the Sea God. Your father’s bitterest rival is Zeus, Lord of the Sky. Your mother knew better than to trust you in an airplane. You would be in Zeus’s domain. You would never come down again alive.”

—The Lightning Thief

This is Zeus's usual outlook:

“I have spared him once already,” Zeus grumbled. “Daring to fly through my domain … pah! I should have blasted him out of the sky for his impudence.”

—The Lightning Thief

Flying on a pegasus may be safer, though

However, Percy can seemingly fly fairly high on a pegasus:

The thing about flying on a pegasus during the daytime is that if you're not careful, you can cause a serious traffic accident on the Long Island Expressway. I had to keep Blackjack up in the clouds, which were, fortunately, pretty low in the winter.

—The Titan's Curse

It's difficult to say whether Percy appreciates the clouds being low because he fears the wrath of Zeus, or because it is very cold further up.

When Percy flies to Olympus (on Blackjack) he remarks on how dangerous flying is, showing that Riordan has not forgotten:

Flying was bad enough for a son of Poseidon, but flying straight up to Zeus's palace, with thunder and lightning swirling around it, was even worse.

The mitigating factor in flying on a pegasus probably is that Poseidon has dominion over horses, which might mean that Percy is then also in Poseidon's domain (and thus that Zeus is less inclined to kill him).

That's the problem with being Poseidon's son: since he created horses out of sea foam, I can understand most equestrian animals, but they can understand me, too.

—The Titan's Curse

The only times Percy flies and is not on a pegasus, there are mitigating circumstances:

1. In The Lightning Thief, he is returning Zeus's master bolt (which the latter would not want to damage or destroy, as noted by Poseidon).
2. In The Titan's Curse, he and his companions are picked up by a pair of statues in response to Thalia Grace's prayer to Zeus. So this can be seen as a favor to Thalia from Zeus—not to mention, Thalia and Percy are being held by the same statue.

Answer 2

Percy considers himself safe because horses are Poseidon's domain.

From The Sea of Monsters novel (emphasis mine):

Being the son of the sea god, I never liked going into the air. My dad had this rivalry with Zeus, so I tried to stay out of the lord of the sky's domain as much as possible. But riding a winged horse felt different. It didn't make me nearly as nervous as being in an airplane. Maybe that was because my dad created horses out of sea foam, so the pegasi were sort of... neutral territory.

Answer 3

I believe that maybe there's a line on how high Percy can fly, I believe that when flying on Blackjack, he doesn't reach that line of limit. This is however, my own opinion. Maybe Riordan forgot about this as well when he wrote the book.