Route reliability record
SAN→SFO
San Diego to San Francisco
- Flights
- 6,583
- Period
- July 2025 to June 2026
- Distance
- 447 mi
- Carriers
- 5
This route draws a C. About 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 6,583 flights, of which United Airlines flew 2,598 at 70.6% on time.
United Airlines is the most reliable of the three carriers covered here at 70.6% on time across 2,598 flights.
Key figures
On time
65.0%
Arrivals under 15 minutes late, of 6,467 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
1.26%
National rate is 1.81%
Best carrier
United
70.6% on time across 2,598 flights
These figures cover 6,583 flights between July 2025 and June 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.
Carrier by carrier
Which airline is most reliable on SAN to SFO
The choice of carrier is not cosmetic here. United Airlines arrives on time 70.6% 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 | 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− |
The spread between United 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
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,124 flights78.9%
- 8am–11am1,230 flights62.9%
- 11am–2pm1,085 flights65.2%
- 2pm–5pm1,055 flights69.6%
- 5pm–8pm1,157 flights58.0%
- 8pm–5am932 flights53.7%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 53.7% on time, against 78.9% 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 8am–11am window is the busiest, with 1,230 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 44 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 38.8% on time, 44 points below March, the best at 83.1%. 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. October was the busiest month here, with 662 flights.
Across the week, Tuesday is the strongest day at 74.5% on time and Thursday the weakest at 59.8%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. National Airspace System accounts for 48% of the 139,000 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.
- 48%National Airspace System
- 34%Late-arriving aircraft
- 16%Carrier
- 2%Extreme weather
- 0%Security
48% 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 67,000 minutes out of 139,000, against a national NAS share of 21%. The split is drawn from 139,206 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 78.9% on time here.
Cancellations sit at 1.26% against a national 1.81%, which is ordinary. Diversions add another 0.50%.
Connections and stage length
What a delay here actually costs
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 8.1% 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 runs 66.6% on time across 6,548 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 6,583 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 83.1% on time and June 38.8%, a swing of 44 points. If the dates move at all, move them out of June before you think about anything else. 6,467 completed flights over 12 months sit behind that.
Common questions
SAN to SFO questions
How often is SAN to SFO delayed?
About 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 35.0% of the 6,583 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SAN to SFO?
United Airlines leads at 70.6% on time across 2,598 flights. Southwest Airlines is at the other end on 58.4%, a gap of 12 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 SAN to SFO?
The 5am–8am departure window is the strongest at 78.9% on time. The 8pm–5am window is the weakest at 53.7%, 25 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 SAN to SFO?
June is the weakest month at 38.8% on time, compared with 83.1% in March. 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
- SFO to SAN — the return legseparate record
- San Diego International (SAN) delay statistics
- San Francisco International (SFO) delay statistics
- United Airlines on-time record70.6%
- SkyWest Airlines on-time record68.0%
- Southwest Airlines on-time record58.4%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SAN to SFO and SFO to SAN are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.