How to undo Auto-Pause

For instance, if i wanted to surf the web and fly from new york to los anglesas, I wuold simply press alt+enter to get the game in a small window.

But, as soon as i click outside of the game window, it automatically pauses!

Does microsoft really think that 100% of our attention has to be on the simulation? The flight takes over half a day!

How do you turn auto pause off?

THanks