Circling above London and reading this:

There was a brilliant flash.
There was utter darkness.
There was a soft floor under Rincewind’s feet, a pink light around him, and the sudden shocked cries of many people.
He looked around wildly. He was standing in some kind of tunnel, which was mostly filled with seats in which outlandishly-dressed people had been strapped. They were all shouting at him.
“Wake up,” he hissed. “Help me!”
Dragging the still-unconscious tourist with him he backed away from the mob until his free hand found an oddly-shaped door handle. He twisted it and ducked through, then slammed it hard. He stared around the new room in which he found himself and met the terrified gaze of a young woman who dropped the tray she was holding and screamed.
It sounded like the sort of scream that brings muscular help. Rincewind, awash with fear-distilled adrenalin, turned and barged past her. There were more seats here, and the people in them ducked as he dragged Twoflower urgently along the central gangway. Beyond the rows of seats were little windows. Beyond the windows, against a background of fleecy clouds, was a dragon’s wing. It was silver.