On Friday night I was in my back garden about 10pm taking advantage of a very clear dark sky (a gap in the weather) and saw several satellites going over in various directions.
One, much brighter than the others (think twice the luminecense of Jupiter and about the same size), caught my eye as it faded out. Not unusual as it looked to be in low orbit due to its speed and brightness and it must have just passed out of the suns rays.
Then after 15 seconds it came back, stayed illuminated for about 5 seconds before fading again, making it's way across the skies. About 10-15 seconds later it would, once more return. I followed it's west-east course until it finally went beyond my sight.
After a bit of internet-looky it appears that some satellites, once their fuel is expended, begin to tumble before re-entering the atmosphere creating the effect I saw.
Never seen it before, and I think it is, for a casual sky gazer, going to be a once in a lifetime event. Still, if it's still up there some of you may get to see it and at least you wont thave to think 'aliens!'.
ETA - A few candidates here -
Upcoming and Recent Decays and Re-entries - eventually air drag, gravity or retro-fire mean that a spacecraft or satellite is no longer able to stay in orbit. It re-enters the atmosphere to be destroyed or make a safe landing.