SFOAPR

The weak window here is the middle of the day, not the evening: 11am–2pm runs 59.5% on time against 94.6% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 8am–11am window is the busiest, with 3,022 flights scheduled in it.

Across the week, Tuesday is the strongest day at 80.7% on time and Monday the weakest at 68.2%. 13 points is a smaller lever than departure hour, but it is free.

The spread between United and Southwest is 30 points, wide enough that it should decide the booking. On a hundred trips that is 30 more arrivals inside the on-time window.

46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 195,000 reported delay minutes here, that single category outweighs weather by 28 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 194,855 reported delay minutes.

Cancellations are rare at 0.70%, below the national 0.90% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

7.3% of arrivals land an hour or more late, close to the national 6.4%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.