Route reliability record

SFO→SAN

San Francisco to San Diego

Flights: 6,548
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 6,548 flights, of which United Airlines flew 2,598 at 76.2% on time.

United Airlines is the most reliable of the three carriers covered here at 76.2% on time across 2,598 flights.

On time

66.6%

Arrivals under 15 minutes late, of 6,457 completed flights

Avg delay

59 min

Across delayed arrivals only, not all flights

Cancelled

1.13%

National rate is 1.81%

Best carrier

United

76.2% on time across 2,598 flights

These figures cover 6,548 flights between July 2025 and June 2026. Beyond the headline rate, 11.6% 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 SFO to SAN

The choice of carrier is not cosmetic here. United Airlines arrives on time 76.2% 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.

On-time performance by carrier on SFO to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	304	88.8%	49 min	0.33%	A+
United Airlines	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 United and Southwest is 23 points, wide enough that it should decide the booking. On a hundred trips that is 23 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 34 points, against 23 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,052 flights91.1%
8am–11am1,219 flights67.7%
11am–2pm1,131 flights59.7%
2pm–5pm1,168 flights56.9%
5pm–8pm1,124 flights62.7%
8pm–5am854 flights62.2%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.1% of the time, against 56.9% for the afternoon window. That is 34 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,219 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 26 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.

Darker means more delays. Figures are on-time percentages.January best, June worst

June is the worst month at 54.1% on time, 26 points below January, the best at 80.3%. 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. October was the busiest month here, with 659 flights.

Across the week, Saturday is the strongest day at 78.3% on time and Monday the weakest at 60.0%. 18 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. Late-arriving aircraft accounts for 50% 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.

Late-arriving aircraft
50%
National Airspace System
28%
Carrier
20%
Extreme weather
1%
Security
0%

50% 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 45 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 127,906 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 91.1% on time here.

Cancellations sit at 1.13% against a national 1.81%, which is ordinary. Diversions add another 0.26%.

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. 11.6% 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 65.0% on time across 6,583 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 6,548 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. January runs 80.3% on time and June 54.1%, a swing of 26 points. If the dates move at all, move them out of June before you think about anything else. 6,457 completed flights over 12 months sit behind that.

Common questions

SFO to SAN questions

How often is SFO to SAN 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 33.4% of the 6,548 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on SFO to SAN?

United Airlines leads at 76.2% on time across 2,598 flights. Southwest Airlines is at the other end on 52.8%, a gap of 23 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 SFO to SAN?

The 5am–8am departure window is the strongest at 91.1% on time. The 2pm–5pm window is the weakest at 56.9%, 34 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 SFO to SAN?

June is the weakest month at 54.1% on time, compared with 80.3% in January. Across the year that is 26 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. SFO to SAN and SAN to SFO 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.

Key figures