Carrier route record
WNSFO→SAN
Southwest Airlines · San Francisco to San Diego
- Flights
- 2,070
- Period
- September 2025 to August 2026
- Share of route
- 31%
- Carriers
- 5
Historical statistics for September 2025 to August 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 47.9% of flights arrive inside the 15-minute window, 29 points worse than the national rate of 77.3%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 2,070 flights. The strongest carrier on the route with a full sample, United Airlines, flew 2,666 at 72.8% on time.
The national on-time rate over the same period is 77.3%, so Southwest on SFO to SAN runs 29 points behind the country as a whole. Across a thousand flights that is about 294 extra late arrivals.
Key figures
On time
47.9%
Arrivals under 15 minutes late, of 2,038 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
1.35%
National rate is 1.89%
Whole route
62.2%
Every carrier on SFO to SAN, 6,723 flights
These figures cover 2,070 flights between September 2025 and August 2026. Beyond the headline rate, 20.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on SFO to SAN
Southwest flew 2,070 of the 6,723 flights on SFO to SAN, about 31% of it. Its 47.9% on time is 14 points worse than the route as a whole, which runs 62.2%. Ranked by on-time rate it is last of five carriers on the route, where the range runs from Alaska at 82.9% to Southwest at 47.9%. 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 72.8% of the time; SkyWest Airlines manages 60.1%. Sample sizes sit next to every figure, because a two-point gap across 1,442 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlinesthin sample | 331 | 82.9% | 44 min | 1.21% | B |
| United Airlines | 2,666 | 72.8% | 54 min | 0.34% | C+ |
| SkyWest Airlines | 1,442 | 60.1% | 59 min | 2.36% | D |
| Frontier Airlinesthin sample | 214 | 48.3% | 95 min | 4.21% | F− |
| Southwest Airlines (this page) | 2,070 | 47.9% | 62 min | 1.35% | F |
The spread between United and SkyWest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
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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 69 points, against 13 points between the best and worst carrier.
- 5am–8am368 flights89.9%
- 8am–11am373 flights51.1%
- 11am–2pm339 flights38.4%
- 2pm–5pm543 flights33.1%
- 5pm–8pm302 flights42.7%
- 8pm–5am145 flights21.0%
Scale runs 15% to 95%.
The 8pm–5am window is where this operation falls apart: 21.0% on time, against 89.9% 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 543 flights scheduled in it.
Across the year
Southwest on SFO to SAN through the year
August is the worst month at 27.9% on time, 46 points below January, the best at 74.3%. 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. August was the busiest month here, with 205 flights.
Across the week, Tuesday is the strongest day at 65.1% on time and Thursday the weakest at 39.1%, a spread of 26 points.
Arrival by arrival
How late Southwest on SFO to SAN runs when it is late
The 1,062 late arrivals split 263 under half an hour, 385 between 30 and 60 minutes, and 414 an hour or more.
- 15+ min early117 flights5.7%
- Within 15 min859 flights42.1%
- 15–29 min late263 flights12.9%
- 30–59 min late385 flights18.9%
- 1–2 hours late303 flights14.9%
- 2+ hours late111 flights5.4%
Scale runs 0% to 100%.
Share of 2,038 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 978 departures that left 15 minutes late or more, only 45 made it up before arrival. In the other direction, 129 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SAN.
The worst days
Worst days for Southwest on SFO to SAN
The latest arrival of the period was on 28 May 2026, 8 hours 28 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 28 May 2026 | 8 hours 28 minutes | Carrier |
| 21 November 2025 | 5 hours 50 minutes | Carrier |
| 21 November 2025 | 5 hours 43 minutes | Late-arriving aircraft |
| 17 April 2026 | 5 hours 15 minutes | Carrier |
| 19 June 2026 | 4 hours 47 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 62% of the 66,000 delay minutes carriers reported here, and the remaining four split what is left.
- 62%Late-arriving aircraft
- 19%Carrier
- 19%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. Across 66,000 reported delay minutes here, that single category outweighs weather by 62 to one. The split is drawn from 66,298 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 89.9% on time here.
Cancellations sit at 1.35% against a national 1.89%, which is ordinary. Diversions add another 0.19%.
Connections and stage length
What a delay here costs
20.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 52.4% on time across 2,070 flights, 5 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 5 points of difference.
The sample behind these figures is 2,070 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 August 27.9%, a swing of 46 points. If the dates move at all, move them out of August before you think about anything else. 2,038 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 SAN82.9%
- United Airlines on SFO to SAN72.8%
- SkyWest Airlines on SFO to SAN60.1%
- Frontier Airlines on SFO to SAN48.3%
- 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.