Carrier route record
WNSFO→SAN
Southwest Airlines · San Francisco to San Diego
- Flights
- 1,935
- Period
- July 2025 to June 2026
- Share of route
- 30%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SFO to SAN earns an F, which is as low as this site's scale goes for a reason. Only 52.8% of flights arrive inside the 15-minute window, 25 points worse than the national rate of 77.6%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 1,935 flights. The strongest carrier on the route with a full sample, United Airlines, flew 2,598 at 76.2% on time.
The national on-time rate over the same period is 77.6%, so Southwest on SFO to SAN runs 25 points behind the country as a whole. Across a thousand flights that is about 248 extra late arrivals.
Key figures
On time
52.8%
Arrivals under 15 minutes late, of 1,907 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
1.24%
National rate is 1.81%
Whole route
66.6%
Every carrier on SFO to SAN, 6,548 flights
These figures cover 1,935 flights between July 2025 and June 2026. Beyond the headline rate, 18.0% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Southwest against every carrier on SFO to SAN
Southwest flew 1,935 of the 6,548 flights on SFO to SAN, about 30% of it. Its 52.8% on time is 14 points worse than the route as a whole, which runs 66.6%. Ranked by on-time rate it is last of five carriers on the route, where the range runs from Alaska at 88.8% to Southwest at 52.8%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. United Airlines arrives on time 76.2% of the time; SkyWest Airlines manages 64.8%. Sample sizes sit next to every figure, because a two-point gap across 1,515 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlinesthin sample | 304 | 88.8% | 49 min | 0.33% | A+ |
| United Airlines | 2,598 | 76.2% | 55 min | 0.46% | B+ |
| SkyWest Airlines | 1,515 | 64.8% | 57 min | 2.05% | D |
| Frontier Airlinesthin sample | 196 | 53.7% | 76 min | 3.06% | F− |
| Southwest Airlines (this page) | 1,935 | 52.8% | 62 min | 1.24% | F |
United leads SkyWest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 67 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am363 flights89.4%
- 8am–11am334 flights56.7%
- 11am–2pm306 flights44.3%
- 2pm–5pm515 flights40.0%
- 5pm–8pm279 flights48.0%
- 8pm–5am138 flights22.1%
Scale runs 15% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 22.1% on time, against 89.4% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 2pm–5pm window is the busiest, with 515 flights scheduled in it.
Across the year
Southwest on SFO to SAN through the year
Delays peak in May, when the on-time rate falls to 31.9%. January is the strongest month at 74.3%. Moving a flexible trip across that boundary buys 42 points. October was the busiest month here, with 192 flights.
Across the week, Tuesday is the strongest day at 69.1% on time and Thursday the weakest at 43.7%. 25 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 56,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 62%Late-arriving aircraft
- 21%Carrier
- 16%National Airspace System
- 0%Extreme weather
- 0%Security
62% 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 56,000 reported delay minutes here, that single category outweighs weather by 62 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 56,196 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.4% on time here.
Cancellations sit at 1.24% against a national 1.81%, which is ordinary. Diversions add another 0.21%.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 18.0% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
At 447 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 58.4% on time across 1,935 flights, 6 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 6 points of difference.
The sample behind these figures is 1,935 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking Southwest on SFO to SAN
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 74.3% on time and May 31.9%, a swing of 42 points. If the dates move at all, move them out of May before you think about anything else. 1,907 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to SAN, every carrier
- Southwest on SAN to SFO, the return leg
- Alaska Airlines on SFO to SAN88.8%
- United Airlines on SFO to SAN76.2%
- SkyWest Airlines on SFO to SAN64.8%
- Frontier Airlines on SFO to SAN53.7%
- Southwest Airlines network-wide record
- San Francisco International (SFO) delay statistics
- San Diego International (SAN) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.