Are you referring to the number of people in the terminals at a given time or the take offs and arrivals? SFO's pretty much busy from 7:15 a.m. on to mid-evening. The first peak departure time is from 7:15 to 8:45, with first peak arrival time from 8:30 to 10:30 a.m., and then it just keeps going. The international flights pick up later in the day. The airport's basically at capacity.