Fairfield, California is about 40 miles northeast of San Francisco. There are three airports that are convenient to the area:
Oakland Airport (OAK) (recommended; about 45 miles away)
Sacramento Airport (SNF) (also recommended; about 50 miles away)
San Francisco Airport (SFO) (least convenient; about 55 miles away)
It is also easy to drive to Fairfield, which is on Interstate 80.