If you landed before 0700 local from KSFO, which is a T1 arrival, we were landing on both runways at the same time. To ensure the airfield doesn't grind to a complete halt, such T1 inbounds land on the northerly runway, and thus those from BIG and OCK doing so need to 'cross' those from LAM and BNN at some point. It is easier to fly over the field and then join the downwind leg on the northerly side, rather than doing the 'red arrows synchro pair crossover' at 10 miles out on the ILS.
Another reason, and which is more likely for your first example, is weather. Frequently there are also other a/c hanging about in our airspace which we need to avoid, including Northolt inbounds and others.
Last edited by Gonzo; 11th October 2005 at 10:23.