Carrier performance at one airport
WN→SFO
Southwest Airlines at San Francisco International
- Departures
- 9,968
- Period
- September 2025 to August 2026
- Routes
- 12
- Rank here
- #8 of 8
Southwest Airlines at San Francisco earns an F+, which is as low as this site's scale goes for a reason. Only 54.8% of flights arrive inside the 15-minute window, 23 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 9,968 flights, of which United Airlines flew 62,048 at 79.8% on time.
Measured against the airport rather than the country, Southwest Airlines runs 21 points behind the 75.3% weighted average across all carriers at SFO. That is the comparison worth making: every operator here works the same runways, the same airspace and the same weather.
Key figures
On time
54.8%
9,851 completed departures
Avg delay
61 min
Across delayed flights only
Cancelled
0.90%
At SFO, this carrier only
Rank here
#8
Of 8 carriers clearing the floor at SFO
These figures cover 9,968 flights between September 2025 and August 2026. Beyond the headline rate, 16.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
Against the competition
Every carrier at SFO, ranked
The choice of carrier is not cosmetic here. United Airlines arrives on time 79.8% of the time; Southwest Airlines manages 54.8%. Sample sizes sit next to every figure, because a two-point gap across 9,968 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 62,048 | 79.8% | 58 min | 0.46% | B+ |
| American Airlines | 11,939 | 76.4% | 102 min | 1.84% | B |
| Delta Air Lines | 13,973 | 75.8% | 67 min | 1.29% | B |
| JetBlue Airways | 4,519 | 75.6% | 76 min | 2.21% | B |
| Alaska Airlines | 10,629 | 75.0% | 55 min | 1.10% | B |
| SkyWest Airlines | 31,536 | 73.8% | 74 min | 1.31% | C |
| Frontier Airlines | 3,581 | 62.7% | 81 min | 2.18% | D |
| Southwest Airlines (this page) | 9,968 | 54.8% | 61 min | 0.90% | F+ |
The spread between United and Southwest is 25 points, wide enough that it should decide the booking. On a hundred trips that is 25 more arrivals inside the on-time window.
Route by route
Where Southwest Airlines flies from SFO
Southwest Airlines operates 12 routes out of SFO with enough volume to report. Route records inside one carrier at one airport still spread widely, because a short shuttle and a transcontinental have very different exposure to a late inbound.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SFO to SAN · San Diego | 2,070 | 47.9% | 62 min | 1.35% | F |
| SFO to LAX · Los Angeles | 1,472 | 56.7% | 62 min | 0.68% | D+ |
| SFO to DEN · Denver | 1,391 | 59.0% | 62 min | 0.79% | D+ |
| SFO to LAS · Las Vegas | 1,314 | 60.6% | 64 min | 0.84% | D+ |
| SFO to PHX · Phoenix | 1,076 | 58.8% | 57 min | 0.56% | D+ |
| SFO to MDW · Chicago | 516 | 73.5% | 43 min | 1.16% | C |
| SFO to BUR · Burbank | 514 | 49.7% | 59 min | 2.33% | F |
| SFO to AUS · Austin | 411 | 40.1% | 64 min | 0.00% | F+ |
| SFO to BWI · Baltimore | 365 | 63.0% | 50 min | 0.82% | D+ |
| SFO to STL · St. Louisthin sample | 342 | 40.2% | 61 min | 0.29% | F+ |
| SFO to BNA · Nashvillethin sample | 312 | 58.4% | 50 min | 0.32% | D+ |
| SFO to DAL · Dallasthin sample | 180 | 20.7% | 64 min | 0.56% | F+ |
Departure window
Best time of day for this operation
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 56 points, against 25 points between the best and worst carrier.
- 5am–8am2,066 flights93.2%
- 8am–11am1,754 flights55.8%
- 11am–2pm1,937 flights37.1%
- 2pm–5pm1,917 flights37.7%
- 5pm–8pm1,148 flights49.2%
- 8pm–5am1,146 flights48.5%
Scale runs 30% to 100%.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 37.1% on time against 93.2% 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 5am–8am window is the busiest, with 2,066 flights scheduled in it.
Across the year
Seasonal pattern
June is the worst month at 36.1% on time, 44 points below January, the best at 79.8%. 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. July was the busiest month here, with 1,010 flights.
Delay causes
What holds this operation up
- 66%Late-arriving aircraft
- 20%Carrier
- 13%National Airspace System
- 0%Extreme weather
- 0%Security
66% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 270,000 reported delay minutes here, that single category outweighs weather by 66 to one. The split is drawn from 269,596 reported delay minutes.
Cancellations sit at 0.90% against a national 1.89%, which is ordinary. Diversions add another 0.27%.
16.9% 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.
The sample behind these figures is 9,968 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.
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 79.8% on time and June 36.1%, a swing of 44 points. If the dates move at all, move them out of June before you think about anything else. 9,851 completed flights over 12 months sit behind that.
Common questions
Southwest Airlines at SFO
How often is Southwest Airlines at SFO delayed?
Close to half of flights arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 45.2% of the 9,968 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on Southwest Airlines at SFO?
United Airlines leads at 79.8% on time across 62,048 flights. Southwest Airlines is at the other end on 54.8%, a gap of 25 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on Southwest Airlines at SFO?
The 5am–8am departure window is the strongest at 93.2% on time. The 11am–2pm window is the weakest at 37.1%, 56 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on Southwest Airlines at SFO?
June is the weakest month at 36.1% on time, compared with 79.8% in January. Across the year that is 44 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
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.