Carrier route record
UASFO→SAN
United Airlines · San Francisco to San Diego
- Flights
- 2,666
- Period
- September 2025 to August 2026
- Share of route
- 40%
- Carriers
- 5
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on SFO to SAN sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 2,666 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,442 at 60.1% on time.
The national on-time rate over the same period is 77.3%, so United on SFO to SAN runs 5 points behind the country as a whole. Across a thousand flights that is about 45 extra late arrivals.
Key figures
On time
72.8%
Arrivals under 15 minutes late, of 2,648 completed flights
Avg delay
54 min
Across delayed arrivals only, not all flights
Cancelled
0.34%
National rate is 1.89%
Whole route
62.2%
Every carrier on SFO to SAN, 6,723 flights
These figures cover 2,666 flights between September 2025 and August 2026. Beyond the headline rate, 8.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
United against every carrier on SFO to SAN
United flew 2,666 of the 6,723 flights on SFO to SAN, about 40% of it. Its 72.8% on time is 11 points better than the route as a whole, which runs 62.2%. Ranked by on-time rate it is number two 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. SkyWest Airlines arrives on time 60.1% of the time; Southwest Airlines manages 47.9%. Sample sizes sit next to every figure, because a two-point gap across 2,070 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 (this page) | 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 | 2,070 | 47.9% | 62 min | 1.35% | F |
The spread between SkyWest and Southwest is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 more arrivals inside the on-time window.
Flight by flight
United flight numbers on SFO to SAN
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Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 32 points, against 12 points between the best and worst carrier.
- 5am–8am262 flights94.6%
- 8am–11am504 flights75.1%
- 11am–2pm469 flights70.9%
- 2pm–5pm447 flights62.2%
- 5pm–8pm474 flights67.9%
- 8pm–5am510 flights74.8%
Scale runs 55% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.6% of the time, against 62.2% for the afternoon window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 510 flights scheduled in it.
Across the year
United on SFO to SAN through the year
August is the worst month at 56.0% on time, 29 points below September, the best at 85.3%. 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 257 flights.
Across the week, Saturday is the strongest day at 84.2% on time and Monday the weakest at 65.1%, a spread of 19 points.
Arrival by arrival
How late United on SFO to SAN runs when it is late
The 720 late arrivals split 253 under half an hour, 256 between 30 and 60 minutes, and 211 an hour or more.
- 15+ min early499 flights18.8%
- Within 15 min1,429 flights54.0%
- 15–29 min late253 flights9.6%
- 30–59 min late256 flights9.7%
- 1–2 hours late155 flights5.9%
- 2+ hours late56 flights2.1%
Scale runs 0% to 100%.
Share of 2,648 completed flights by arrival against schedule.
112 of 650 late departures made up the time and arrived on time, 17% of them. In the other direction, 182 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 United on SFO to SAN
The latest arrival of the period was on 18 December 2025, 7 hours 29 minutes behind schedule; most of its delay minutes were filed as extreme weather. The five worst days are spread across December, October, February, August and January, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 18 December 2025 | 7 hours 29 minutes | Extreme weather |
| 13 October 2025 | 7 hours 11 minutes | Extreme weather |
| 14 February 2026 | 5 hours 46 minutes | National Airspace System |
| 20 August 2026 | 5 hours 9 minutes | Late-arriving aircraft |
| 5 January 2026 | 4 hours 42 minutes | Late-arriving aircraft |
Delay causes
Why United runs late on this route
Late-arriving aircraft accounts for 46% of the 39,000 delay minutes carriers reported here, and the remaining four split what is left.
- 46%Late-arriving aircraft
- 33%National Airspace System
- 19%Carrier
- 2%Extreme weather
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 39,000 reported delay minutes here, that single category outweighs weather by 22 to one. The split is drawn from 38,655 reported delay minutes.
33% 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 13,000 minutes out of 39,000, against a national NAS share of 21%.
Cancellations are rare at 0.34%, below the national 1.89% 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.
Connections and stage length
What a delay here costs
8.0% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 55 minutes, which a normal layover absorbs.
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 67.2% on time across 2,666 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 2,666 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 United on SFO to SAN
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 85.3% on time and August 56.0%, a swing of 29 points. If the dates move at all, move them out of August before you think about anything else. 2,648 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to SAN, every carrier
- United on SAN to SFO, the return leg
- Alaska Airlines on SFO to SAN82.9%
- SkyWest Airlines on SFO to SAN60.1%
- Frontier Airlines on SFO to SAN48.3%
- Southwest Airlines on SFO to SAN47.9%
- United Airlines network-wide record
- San Francisco International (SFO) delay statistics
- San Diego International (SAN) delay statistics
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
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.