Carrier route record
UASAN→SFO
United Airlines · San Diego to San Francisco
- Flights
- 2,598
- Period
- July 2025 to June 2026
- Share of route
- 39%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SAN to SFO sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 2,598 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,551 at 68.0% on time.
The national on-time rate over the same period is 77.6%, so United on SAN to SFO runs 7 points behind the country as a whole. Across a thousand flights that is about 70 extra late arrivals.
Key figures
On time
70.6%
Arrivals under 15 minutes late, of 2,581 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
0.65%
National rate is 1.81%
Whole route
65.0%
Every carrier on SAN to SFO, 6,583 flights
These figures cover 2,598 flights between July 2025 and June 2026. Beyond the headline rate, 9.4% 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.
Carrier by carrier
United against every carrier on SAN to SFO
United flew 2,598 of the 6,583 flights on SAN to SFO, about 39% of it. Its 70.6% on time is 6 points better than the route as a whole, which runs 65.0%. Ranked by on-time rate it is first of five carriers on the route, where the range runs from United at 70.6% to Frontier at 47.0%. 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 68.0% of the time; Southwest Airlines manages 58.4%. 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 |
|---|---|---|---|---|---|
| United Airlines (this page) | 2,598 | 70.6% | 60 min | 0.65% | C+ |
| SkyWest Airlines | 1,551 | 68.0% | 62 min | 1.74% | C |
| Southwest Airlines | 1,935 | 58.4% | 61 min | 1.09% | D |
| Alaska Airlinesthin sample | 303 | 54.0% | 55 min | 0.99% | F+ |
| Frontier Airlinesthin sample | 196 | 47.0% | 83 min | 7.65% | F− |
SkyWest leads Southwest by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
United flight numbers on SAN to SFO
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 20 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am524 flights79.7%
- 8am–11am508 flights67.9%
- 11am–2pm370 flights67.8%
- 2pm–5pm475 flights76.5%
- 5pm–8pm522 flights64.7%
- 8pm–5am199 flights59.7%
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 59.7% on time, against 79.7% 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 5am–8am window is the busiest, with 524 flights scheduled in it.
Across the year
United on SAN to SFO through the year
Delays peak in May, when the on-time rate falls to 49.1%. March is the strongest month at 89.3%. Moving a flexible trip across that boundary buys 40 points. April was the busiest month here, with 240 flights.
Across the week, Tuesday is the strongest day at 77.1% on time and Thursday the weakest at 66.8%. 10 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. National Airspace System accounts for 56% of the 46,000 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.
- 56%National Airspace System
- 26%Late-arriving aircraft
- 14%Carrier
- 3%Extreme weather
56% 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 25,000 minutes out of 46,000, against a national NAS share of 21%. The split is drawn from 45,723 reported delay minutes.
Cancellations are rare at 0.65%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.4% of arrivals land a full hour or more behind schedule, against 8.1% 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.
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 76.2% on time across 2,598 flights, 6 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 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 SAN to SFO
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 89.3% on time and May 49.1%, a swing of 40 points. If the dates move at all, move them out of May before you think about anything else. 2,581 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to SFO, every carrier
- United on SFO to SAN, the return leg
- SkyWest Airlines on SAN to SFO68.0%
- Southwest Airlines on SAN to SFO58.4%
- Alaska Airlines on SAN to SFO54.0%
- Frontier Airlines on SAN to SFO47.0%
- United Airlines network-wide record
- San Diego International (SAN) delay statistics
- San Francisco International (SFO) delay statistics
- How often a connection fails at the major US hubs
- The best time of day to fly, according to 7.04 million flight records
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.