But you can only reach them by car, so you might as well live in the suburbs.

CNN: We'll always have Paris

One recent Saturday night at Philadelphia airport, en route from her main home in Florida (when you travel as much as Ms Knapp, you might as well live where you want) to Frankfurt and London, she bumped into her opposite number at McKinsey, a management consultancy, who was on her way to New Delhi.

ECONOMIST: On a wing and a hotel room