Route reliability record

SJC→SAN

San Jose to San Diego

Flights: 4,979
Period: July 2025 to June 2026
Distance: 417 mi
Carriers: 4

This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land roughly 45 minutes behind schedule. That rests on 4,979 flights, of which SkyWest Airlines flew 1,166 at 77.1% on time.

The national on-time rate over the same period is 77.6%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 52 extra late arrivals.

On time

72.4%

Arrivals under 15 minutes late, of 4,920 completed flights

Avg delay

46 min

Across delayed arrivals only, not all flights

Cancelled

1.02%

National rate is 1.81%

Best carrier

SkyWest

77.1% on time across 1,166 flights

These figures cover 4,979 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Carrier by carrier

Which airline is most reliable on SJC to SAN

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 77.1% of the time; Southwest Airlines manages 70.7%. Sample sizes sit next to every figure, because a two-point gap across 3,740 flights means less than a ten-point one.

On-time performance by carrier on SJC to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	49	91.8%	63 min	0.00%	A+
SkyWest Airlines	1,166	77.1%	49 min	1.20%	B
Spirit Airlinesthin sample	24	70.8%	62 min	0.00%	C+
Southwest Airlines	3,740	70.7%	45 min	0.99%	C+

SkyWest leads Southwest by 6 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 30 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am789 flights90.6%
8am–11am1,121 flights79.4%
11am–2pm830 flights70.9%
2pm–5pm870 flights66.6%
5pm–8pm1,010 flights60.3%
8pm–5am359 flights62.0%

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

The 5pm–8pm window is where this operation falls apart: 60.3% on time, against 90.6% 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 1,121 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 22 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 59.7% on time, 22 points below January, the best at 81.4%. 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. July was the busiest month here, with 471 flights.

Across the week, Tuesday is the strongest day at 84.9% on time and Friday the weakest at 60.5%. 24 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 63,000 reported delay minutes.

Late-arriving aircraft
41%
National Airspace System
36%
Carrier
21%
Extreme weather
2%
Security
0%

41% 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 63,000 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 62,640 reported delay minutes.

36% 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 23,000 minutes out of 63,000, against a national NAS share of 21%.

Cancellations sit at 1.02% against a national 1.81%, which is ordinary. Diversions add another 0.16%.

Connections and stage length

What a delay here actually costs

6.2% 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 are the roughly 45 minutes kind, which a normal layover absorbs.

At 417 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 77.6% on time across 4,953 flights, 5 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 5 points of difference.

The sample behind these figures is 4,979 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 81.4% on time and June 59.7%, a swing of 22 points. If the dates move at all, move them out of June before you think about anything else. 4,920 completed flights over 12 months sit behind that.

Common questions

SJC to SAN questions

How often is SJC to SAN delayed?

Roughly one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.6% of the 4,979 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 45 minutes on average.

Which airline is most reliable on SJC to SAN?

SkyWest Airlines leads at 77.1% on time across 1,166 flights. Southwest Airlines is at the other end on 70.7%, a gap of 6 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 SJC to SAN?

The 5am–8am departure window is the strongest at 90.6% on time. The 5pm–8pm window is the weakest at 60.3%, 30 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 SJC to SAN?

June is the weakest month at 59.7% on time, compared with 81.4% in January. Across the year that is 22 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. SJC to SAN and SAN to SJC 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