My latest colleague, the 747-400, has now been through the engine removal stage of disassembly - very similar to my first hand account back in April. I figure we've been branded buddies for life, and "end of life", by Boeing and our 747 status. However, there is at least one remarkable fact that might be of interest to all you passengers. Check out this Auxiliary Power Unit... I think of it as the "little engine that could & DOES". This secondary power unit, located at the rear of the aircraft, often operates the systems that keep you comfortable while the plane is grounded at the gate - before departure and after arrival - including the heating & cooling systems along with electrical systems and the ever-critical lavatories.
If you wonder... why don't I "tout" my very own APU? As a cargo aircraft, I've got one - it's just not quite as glam keeping cargo cool.