why planes dont fly

In one of the classic understatements of aviation history, Eric Moody turned on the flight intercom of his British Airways 747 and reported to his 248 passengers:

Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them under control. I trust you are not in too much distress.
http://blog.ametsoc.org/uncategorized/the-long-and-short-of-volcanic-effects/