After leaving Karachi, the event with The Sun will occur. When Kakyoin decides to inspect the sun to determine whether or not it's a Stand, a battle will start. Normally, this battle will be with Kakyoin only, but if the protagonist has a long-range Stand (Miracles, Quicksilver, Wildhearts, Adam Ant, Ocean Blue, or Mr. Big) you can choose to join in. Defeat it to get EXP and items and skip to the end of the event, or run away to watch the scene unfold as normal.
If your FP with Kakyoin is 7 or more, when Kakyoin attempts to convince the group that the baby is a Stand user, you will be given the option to believe him. Doing so will raise his FP by 3, and allow Kakyoin to fight Death 13 1v1. If your FP with Kakyoin is 10 or more before the aforementioned FP bonus, he'll give you the Charm of Karachi, an equippable item, and you'll be able to fight a battle with Kakyoin vs. Death 13 and Fake Star Platinum. Choosing not to believe him will give you the option to skip the event, as this route does not lead to a battle.
Requirements: Stand is Cardigans or Carpenters, or Josuke is protagonist
If you meet one of the above requirements, before departing on the propeller plane, you'll be given the option to either heal the baby or fix the spare plane, depending on your Stand. Doing so will allow you to skip the Death 13 battle altogether, but safe travels to the Red Sea aren't in the cards for the party, and you'll be attacked by another Stand user in midair. A battle will start that will result in a Game Over if not ended within 10 turns.
This event differs greatly if you're playing as Josuke.
Range: L. Each turn, it'll randomly inflict Mummy, Darkness, or Dizzy on the party, and its Sun Laser also has a high chance to inflict BlowBack.
BOSS: Death 13 (User: Mannish Boy)
Range: S. Can only be fought if the protagonist chose to believe Kakyoin's story. Appears with Fake Star Platinum.
BOSS: Fake Star Platinum
Range: M, but uses close-range attacks. Make sure to defeat it for its Starplatodine.
BOSS: The Tyde
The Tyde's range is L-M, the plane's range is L. If 10 turns pass, it's an instant game over. Might seem like an easy fight at first glance, but it has stun moves that paralyze the entire party, can use medicine to heal itself, and will almost always stay at range L. Additionally, if your character is afraid of heights they will start with Fear. Since The Tyde (M) and the Tyde (L) have separate drops, it's possible to get 2 Sunlight Remedies from the battle.