Carrier performance at one airport
WN→SFO
Southwest Airlines at San Francisco International
- Departures
- 9,132
- Period
- June 2025 to May 2026
- Routes
- 12
- Rank here
- #9 of 9
Southwest Airlines at San Francisco draws a D+. Roughly one flight in three arrive 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 9,132 flights, of which United Airlines flew 59,976 at 81.7% on time.
Measured against the airport rather than the country, Southwest Airlines runs 16 points behind the 78.3% 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
61.9%
9,043 completed departures
Avg delay
58 min
Across delayed flights only
Cancelled
0.79%
At SFO, this carrier only
Rank here
#9
Of 9 carriers clearing the floor at SFO
These figures cover 9,132 flights between June 2025 and May 2026. Beyond the headline rate, 12.6% 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.
Against the competition
Every carrier at SFO, ranked
The choice of carrier is not cosmetic here. United Airlines arrives on time 81.7% of the time; Southwest Airlines manages 61.9%. Sample sizes sit next to every figure, because a two-point gap across 9,132 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 59,976 | 81.7% | 59 min | 0.56% | B+ |
| Delta Air Lines | 13,738 | 80.0% | 70 min | 1.21% | B |
| JetBlue Airways | 4,340 | 80.0% | 75 min | 1.57% | B |
| American Airlines | 11,739 | 78.5% | 101 min | 1.88% | B |
| SkyWest Airlines | 32,426 | 77.8% | 74 min | 1.19% | B |
| Alaska Airlines | 10,622 | 76.1% | 55 min | 1.13% | B |
| Hawaiian Airlines | 593 | 75.6% | 65 min | 1.85% | B |
| Frontier Airlines | 3,323 | 65.5% | 83 min | 1.93% | C |
| Southwest Airlines (this page) | 9,132 | 61.9% | 58 min | 0.79% | D+ |
The spread between United and Southwest is 20 points, wide enough that it should decide the booking. On a hundred trips that is 20 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 | 1,886 | 55.3% | 60 min | 1.06% | D |
| SFO to DEN · Denver | 1,455 | 61.7% | 55 min | 0.82% | D+ |
| SFO to LAX · Los Angeles | 1,325 | 64.9% | 60 min | 0.60% | D+ |
| SFO to LAS · Las Vegas | 1,313 | 69.2% | 62 min | 0.53% | C+ |
| SFO to PHX · Phoenix | 1,079 | 63.2% | 56 min | 0.56% | D+ |
| SFO to MDW · Chicago | 425 | 78.1% | 39 min | 1.41% | B |
| SFO to BWI · Baltimorethin sample | 361 | 69.3% | 45 min | 0.83% | C+ |
| SFO to STL · St. Louisthin sample | 342 | 54.3% | 58 min | 0.00% | F+ |
| SFO to BNA · Nashvillethin sample | 307 | 61.3% | 49 min | 0.33% | D+ |
| SFO to AUS · Austinthin sample | 295 | 47.5% | 63 min | 0.00% | F+ |
| SFO to BUR · Burbankthin sample | 251 | 56.4% | 68 min | 3.19% | D− |
| SFO to DAL · Dallasthin sample | 88 | 19.5% | 69 min | 1.14% | 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 46 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,995 flights93.0%
- 8am–11am1,544 flights64.8%
- 11am–2pm1,794 flights47.3%
- 2pm–5pm1,760 flights46.9%
- 5pm–8pm1,010 flights57.0%
- 8pm–5am1,029 flights53.0%
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.0% of the time, against 46.9% for the afternoon window. That is 46 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
Seasonal pattern
Delays peak in May, when the on-time rate falls to 44.4%. January is the strongest month at 79.8%. Moving a flexible trip across that boundary buys 35 points.
Delay causes
What holds this operation up
- 62%Late-arriving aircraft
- 22%Carrier
- 15%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 200,000 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.
Cancellations are rare at 0.79%, below the national 1.80% 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.
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.6% of arrivals land a full hour or more behind schedule, against 8.2% 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.
The sample behind these figures is 9,132 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 May 44.4%, a swing of 35 points. If the dates move at all, move them out of May before you think about anything else.
Common questions
Southwest Airlines at SFO
How often is Southwest Airlines at SFO delayed?
Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 38.1% of the 9,132 flights in this analysis, against 22.6% 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 81.7% on time across 59,976 flights. Southwest Airlines is at the other end on 61.9%, a gap of 20 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 93.0% on time. The 2pm–5pm window is the weakest at 46.9%, 46 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 May delays on Southwest Airlines at SFO?
May is the weakest month at 44.4% on time, compared with 79.8% in January. Across the year that is 35 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
- Southwest Airlines network-wide record
- San Francisco International (SFO) all carriers
- SFO to SAN route record55.3%
- SFO to DEN route record61.7%
- SFO to LAX route record64.9%
- SFO to LAS route record69.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.