The thing is that an aircraft uses so-called "bleed air" from the engines to control air condition inside the aircraft. Jet engines only use some of the air for combustion inside the engine. The remaining air is "bypassed" around the engine (helps cooling the engine). Some of this air is then taken ("bled") from the engine into the cabin (via air conditioning equipment, of course) to control the cabin environment (humidity, pressure, temperature). http://en.wikipedia.org/wiki/Bleed_air

Bye Bye Blackbird http://www.youtube.com/watch?v=ji4nZ5k82uk&feature=related Please note, that all aircraft are certified for flying using one engine only.

Fast food: From chicken to nugget under one second: http://www.youtube.com/watch?v=_jfXX7qppbc http://www.youtube.com/watch?v=y2OS2pwrZTI&feature=PlayList&p=63A77080B0A969AC&playnext=1&index=21