Carrier route record
UASFO→SAN
United Airlines · San Francisco to San Diego
- Flights
- 2,598
- Period
- July 2025 to June 2026
- Share of route
- 40%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SFO to SAN lands a B+, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 2,598 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,515 at 64.8% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on SFO to SAN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.2%
Arrivals under 15 minutes late, of 2,577 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.46%
National rate is 1.81%
Whole route
66.6%
Every carrier on SFO to SAN, 6,548 flights
These figures cover 2,598 flights between July 2025 and June 2026. The median arrival is 4 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
United against every carrier on SFO to SAN
United flew 2,598 of the 6,548 flights on SFO to SAN, about 40% of it. Its 76.2% on time is 10 points better than the route as a whole, which runs 66.6%. Ranked by on-time rate it is number two of five carriers on the route, where the range runs from Alaska at 88.8% to Southwest at 52.8%. 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 64.8% of the time; Southwest Airlines manages 52.8%. Sample sizes sit next to every figure, because a two-point gap across 1,935 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlinesthin sample | 304 | 88.8% | 49 min | 0.33% | A+ |
| United Airlines (this page) | 2,598 | 76.2% | 55 min | 0.46% | B+ |
| SkyWest Airlines | 1,515 | 64.8% | 57 min | 2.05% | D |
| Frontier Airlinesthin sample | 196 | 53.7% | 76 min | 3.06% | F− |
| Southwest Airlines | 1,935 | 52.8% | 62 min | 1.24% | 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.
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 23 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am275 flights93.4%
- 8am–11am433 flights80.8%
- 11am–2pm513 flights72.0%
- 2pm–5pm400 flights71.6%
- 5pm–8pm474 flights70.7%
- 8pm–5am503 flights75.8%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.4% of the time, against 70.7% for the evening window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 513 flights scheduled in it.
Across the year
United on SFO to SAN through the year
September is the best month on the calendar at 85.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. April was the busiest month here, with 240 flights.
Across the week, Saturday is the strongest day at 85.5% on time and Monday the weakest at 70.4%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 34,000 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
- 27%National Airspace System
- 24%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. That is a cascade, and cascades start small and grow through the day. Across 34,000 reported delay minutes here, that single category outweighs weather by 19 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 33,759 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 93.4% on time here.
Cancellations are rare at 0.46%, below the national 1.81% 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
7.0% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, 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 70.6% on time across 2,598 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 2,598 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 November 65.1%, a swing of 20 points. If the dates move at all, move them out of November before you think about anything else. 2,577 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 SAN88.8%
- SkyWest Airlines on SFO to SAN64.8%
- Frontier Airlines on SFO to SAN53.7%
- Southwest Airlines on SFO to SAN52.8%
- 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.