I was waiting for one specific jet at SEA (which has long ago made an appearance on this blog) but, while I was hanging around, I was shooting different angles up the approach.  In a few shots I could see a number of aircraft lined up on the approach or turning on to it.  I played around with seeing how many I might get in one shot.  It needed relatively clear air to get the more distant planes visible.  A hazy day would not do the trick.