An analysis is made of an advection fog process that induced serious delay and cancellation of flights in the Capital Airport on 21 February 2007 in the aspects of synoptic situation and physical parameter fields, in compared with the typical advection fog process on 16 January 2000. The statistical analysis and comparison are performed on all the advection fog processes occurred in the Capital Airport from 2000 to 2007, to find out the characteristics of the advection fog weather. Some forecasting hints of advection fogs over the Capital Airport are summarized and presented: under the weak weather situation, if there exists a large fog area in the southeast and ground temperature increases abnormally or keeps warm for a long time resulted from warm advection before dawn in both Tongxian and Capital Airport, the wind direction at Capital Airport turning to east or southeast as well, the advection fog can be forecasted.