Route reliability record
SAN→SFO
San Diego to San Francisco
- Flights
- 6,543
- Period
- June 2025 to May 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 6,543 flights, of which United Airlines flew 2,585 at 72.9% on time.
United Airlines is the most reliable of the three carriers covered here at 72.9% on time across 2,585 flights.
Key figures
On time
67.7%
Arrivals under 15 minutes late, of 6,450 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
1.13%
National rate is 1.80%
Best carrier
United
72.9% on time across 2,585 flights
These figures cover 6,543 flights between June 2025 and May 2026. Beyond the headline rate, 11.3% 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 72.9% of the time; Southwest Airlines manages 61.5%. Sample sizes sit next to every figure, because a two-point gap across 1,886 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 2,585 | 72.9% | 61 min | 0.66% | C+ |
| SkyWest Airlines | 1,581 | 70.9% | 61 min | 1.58% | C |
| Southwest Airlines | 1,886 | 61.5% | 60 min | 0.95% | D+ |
| Alaska Airlinesthin sample | 303 | 56.0% | 55 min | 0.33% | D+ |
| Frontier Airlinesthin sample | 188 | 49.7% | 85 min | 6.91% | F− |
United leads Southwest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 24 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,138 flights80.3%
- 8am–11am1,252 flights65.9%
- 11am–2pm1,002 flights69.7%
- 2pm–5pm1,064 flights71.3%
- 5pm–8pm1,129 flights61.1%
- 8pm–5am958 flights56.3%
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 56.3% on time, against 80.3% 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.
Across the year
When delays peak on this route
This route's year swings by 40 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.
Delays peak in May, when the on-time rate falls to 42.6%. March is the strongest month at 83.1%. Moving a flexible trip across that boundary buys 40 points.
Across the week, Tuesday is the strongest day at 77.9% on time and Thursday the weakest at 62.3%. 16 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 45% of the 128,000 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.
- 45%National Airspace System
- 36%Late-arriving aircraft
- 17%Carrier
- 2%Extreme weather
- 0%Security
36% 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 128,000 reported delay minutes here, that single category outweighs weather by 15 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.
45% 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 57,000 minutes out of 128,000, against a national NAS share of 21%.
Cancellations sit at 1.13% against a national 1.80%, which is ordinary. Diversions add another 0.29%.
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. 11.3% 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.
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 68.3% on time across 6,524 flights, within half a point 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 6,543 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 May 42.6%, a swing of 40 points. If the dates move at all, move them out of May before you think about anything else.
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 32.3% of the 6,543 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SAN to SFO?
United Airlines leads at 72.9% on time across 2,585 flights. Southwest Airlines is at the other end on 61.5%, a gap of 11 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 80.3% on time. The 8pm–5am window is the weakest at 56.3%, 24 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 SAN to SFO?
May is the weakest month at 42.6% on time, compared with 83.1% in March. Across the year that is 40 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 record72.9%
- SkyWest Airlines on-time record70.9%
- Southwest Airlines on-time record61.5%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 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, June 2025 to May 2026. Updated monthly. How this data is collected.