I have had plenty of chances to shoot the departures from SEA when they are on a northerly flow and the afternoon light provides a good option for the jets.  Previously, I have used the 500mm since it gives good reach but, for the larger jets, as you get the jet abeam your position, it will be too large for 500mm.  The arrival of my 200-800 provided a great new option.  800mm provided a tighter view on the jets after rotation (provided the heat haze is not negating any focal length benefit) and the ability to zoom out means that you can keep the aircraft fully framed throughout the climb out.  I took the lens down when I first had an open afternoon and the right conditions and here are some of the results.  As fall moves towards winter and the heat haze and high sun become less of an issue, this combo should get even better.