San Francisco International Airport (SFO) data on Landings Statistics. Airport data is seasonal in nature, therefore any comparative analyses should be done on a period-over-period basis (i.e. January 2010 vs. January 2009) as opposed to period-to-period (i.e. January 2010 vs. February 2010). It is also important to note that fact and attribute field relationships are not always 1-to-1. For example, Aircraft Landings belonging to United Airlines will appear in multiple attribute fields and are additive, which provides flexibility for the user to derive categorical Aircraft Landings Statistics as desired.