Carrier route record
WNSAN→SFO
Southwest Airlines · San Diego to San Francisco
- Flights
- 1,935
- Period
- July 2025 to June 2026
- Share of route
- 29%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SAN to SFO draws a D. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 1,935 flights. The strongest carrier on the route with a full sample, United Airlines, flew 2,598 at 70.6% on time.
The national on-time rate over the same period is 77.6%, so Southwest on SAN to SFO runs 19 points behind the country as a whole. Across a thousand flights that is about 192 extra late arrivals.
Key figures
On time
58.4%
Arrivals under 15 minutes late, of 1,914 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
1.09%
National rate is 1.81%
Whole route
65.0%
Every carrier on SAN to SFO, 6,583 flights
These figures cover 1,935 flights between July 2025 and June 2026. Beyond the headline rate, 15.4% 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 SAN to SFO
Southwest flew 1,935 of the 6,583 flights on SAN to SFO, about 29% of it. Its 58.4% on time is 7 points worse than the route as a whole, which runs 65.0%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from United at 70.6% to Frontier at 47.0%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 2,598 | 70.6% | 60 min | 0.65% | C+ |
| SkyWest Airlines | 1,551 | 68.0% | 62 min | 1.74% | C |
| Southwest Airlines (this page) | 1,935 | 58.4% | 61 min | 1.09% | D |
| Alaska Airlinesthin sample | 303 | 54.0% | 55 min | 0.99% | F+ |
| Frontier Airlinesthin sample | 196 | 47.0% | 83 min | 7.65% | F− |
No carrier stands out. United tops the table at 70.6%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 53 points, against 3 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am307 flights87.2%
- 8am–11am385 flights61.7%
- 11am–2pm307 flights56.9%
- 2pm–5pm323 flights58.6%
- 5pm–8pm356 flights48.1%
- 8pm–5am257 flights34.5%
Scale runs 25% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 34.5% on time, against 87.2% 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 8am–11am window is the busiest, with 385 flights scheduled in it.
Across the year
Southwest on SAN to SFO through the year
June is the worst month at 29.4% on time, 53 points below January, the best at 82.6%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. October was the busiest month here, with 192 flights.
Across the week, Tuesday is the strongest day at 75.1% on time and Thursday the weakest at 49.8%. 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 46% of the 48,000 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.
- 46%Late-arriving aircraft
- 37%National Airspace System
- 16%Carrier
- 2%Extreme weather
- 0%Security
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 48,000 reported delay minutes here, that single category outweighs weather by 25 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 48,202 reported delay minutes.
37% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 18,000 minutes out of 48,000, against a national NAS share of 21%.
Cancellations sit at 1.09% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
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. 15.4% 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 52.8% on time across 1,935 flights, 6 points below 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 SAN to SFO
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 82.6% on time and June 29.4%, a swing of 53 points. If the dates move at all, move them out of June before you think about anything else. 1,914 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to SFO, every carrier
- Southwest on SFO to SAN, the return leg
- United Airlines on SAN to SFO70.6%
- SkyWest Airlines on SAN to SFO68.0%
- Alaska Airlines on SAN to SFO54.0%
- Frontier Airlines on SAN to SFO47.0%
- Southwest Airlines network-wide record
- San Diego International (SAN) delay statistics
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.