Carrier route record

WNSAN→SJC

Southwest Airlines · San Diego to San Jose

Flights: 3,741
Period: July 2025 to June 2026
Share of route: 76%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on SAN to SJC lands a B+, 2 points worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. That rests on 3,741 flights, with a median arrival 5 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Southwest on SAN to SJC from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

76.0%

Arrivals under 15 minutes late, of 3,709 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.80%

National rate is 1.81%

Whole route

77.6%

Every carrier on SAN to SJC, 4,953 flights

These figures cover 3,741 flights between July 2025 and June 2026. The median arrival is 5 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Southwest against every carrier on SAN to SJC

Southwest flew 3,741 of the 4,953 flights on SAN to SJC, most of the route. Its 76.0% on time is 2 points worse than the route as a whole, which runs 77.6%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from SkyWest at 82.9% to Spirit at 75.0%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on SAN to SJC
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	1,140	82.9%	54 min	1.14%	B
Alaska Airlinesthin sample	48	81.2%	33 min	0.00%	B+
Southwest Airlines (this page)	3,741	76.0%	49 min	0.80%	B+
Spirit Airlinesthin sample	24	75.0%	115 min	0.00%	B+

Departure window

When Southwest runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 33 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am440 flights96.1%
8am–11am783 flights87.0%
11am–2pm671 flights74.1%
2pm–5pm704 flights66.6%
5pm–8pm802 flights69.5%
8pm–5am341 flights62.7%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 62.7% on time, against 96.1% 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 5pm–8pm window is the busiest, with 802 flights scheduled in it.

Across the year

Southwest on SAN to SJC through the year

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

June is the worst month at 60.7% on time, 25 points below January, the best at 85.5%. 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 334 flights.

Across the week, Wednesday is the strongest day at 85.9% on time and Sunday the weakest at 67.5%. 18 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Southwest runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 72% of the 44,000 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
72%
Carrier
23%
National Airspace System
4%
Security
0%
Extreme weather
0%

72% 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 44,000 reported delay minutes here, that single category outweighs weather by 72 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 43,697 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 96.1% on time here.

Cancellations are rare at 0.80%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

5.9% 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 last about 50 minutes, 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 70.7% on time across 3,740 flights, 5 points below 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 3,741 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 Southwest on SAN to SJC

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 85.5% on time and June 60.7%, a swing of 25 points. If the dates move at all, move them out of June before you think about anything else. 3,709 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures