Route reliability record

SJC→SAN

San Jose to San Diego

Flights: 4,990
Period: June 2025 to May 2026
Distance: 417 mi
Carriers: 4

This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.4%. The late ones land roughly 45 minutes behind schedule. That rests on 4,990 flights, of which SkyWest Airlines flew 1,182 at 77.7% on time.

The US average over the same twelve months is 77.4%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

73.8%

Arrivals under 15 minutes late, of 4,929 completed flights

Avg delay

46 min

Across delayed arrivals only, not all flights

Cancelled

1.08%

National rate is 1.80%

Best carrier

SkyWest

77.7% on time across 1,182 flights

These figures cover 4,990 flights between June 2025 and May 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 two carriers here are closely matched: 5 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on SJC to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	19	100.0%	—	0.00%	A+
SkyWest Airlines	1,182	77.7%	51 min	1.27%	B
Southwest Airlines	3,746	72.5%	45 min	1.04%	C
Spirit Airlinesthin sample	43	69.8%	55 min	0.00%	C+

No carrier stands out. SkyWest tops the table at 77.7%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.

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 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am802 flights91.2%
8am–11am1,077 flights80.3%
11am–2pm827 flights73.4%
2pm–5pm918 flights67.5%
5pm–8pm1,005 flights61.6%
8pm–5am361 flights66.8%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 61.6% on time, against 91.2% 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 17 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, December worst

December is the weak month at 64.9% on time, against 81.4% in January. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days.

Across the week, Tuesday is the strongest day at 85.8% on time and Friday the weakest at 61.7%. 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 60,000 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 60,000 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.

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 22,000 minutes out of 60,000, against a national NAS share of 21%.

Cancellations sit at 1.08% against a national 1.80%, which is ordinary. Diversions add another 0.14%.

Connections and stage length

What a delay here actually costs

5.9% of arrivals land an hour or more late, close to the national 8.2%. 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 78.2% on time across 4,980 flights, 4 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 4 points of difference.

The sample behind these figures is 4,990 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 December 64.9%, a swing of 17 points. If the dates move at all, move them out of December before you think about anything else.

Common questions

SJC to SAN questions

How often is SJC to SAN delayed?

About 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 26.2% of the 4,990 flights in this analysis, against 22.6% nationally. Delayed flights are late by roughly 45 minutes on average.

Which airline is most reliable on SJC to SAN?

SkyWest Airlines leads at 77.7% on time across 1,182 flights. Southwest Airlines is at the other end on 72.5%, a gap of 5 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 91.2% on time. The 5pm–8pm window is the weakest at 61.6%, 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 December delays on SJC to SAN?

December is the weakest month at 64.9% on time, compared with 81.4% in January. Across the year that is 17 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, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures