The scene opens with Harry and Hermione standing next to their bags in a Heathrow Airport departure lounge where they are surrounded by people coming and going and standing and sitting near luggage of their own. Ron is nowhere to be seen, because he's in a nearby men's room. Again.
"Harry, what did you tell Ron? He's pale and shaking, and he's thrown up three times since we got here."
"I did what you asked and told him how aeroplanes work."
"How could that make him sick?"
"Hermione, you do realize that we're climbing into a giant tin with wings that's only held up by four engines that are powered by a combustible and potentially explosive liquid, right?"
"...Yes, but it's not like it works 'Because it's magic'."