Carrier route record

WNDEN→SJC

Southwest Airlines · Denver to San Jose

Flights: 1,529
Period: July 2025 to June 2026
Share of route: 59%
Carriers: 3

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

Southwest on DEN to SJC sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,529 flights, with a median arrival 2 minutes late.

The national on-time rate over the same period is 77.6%, so Southwest on DEN to SJC runs 8 points behind the country as a whole. Across a thousand flights that is about 82 extra late arrivals.

On time

69.4%

Arrivals under 15 minutes late, of 1,519 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.65%

National rate is 1.81%

Whole route

74.0%

Every carrier on DEN to SJC, 2,579 flights

These figures cover 1,529 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% 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

Southwest against every carrier on DEN to SJC

Southwest flew 1,529 of the 2,579 flights on DEN to SJC, most of the route. Its 69.4% on time is 5 points worse than the route as a whole, which runs 74.0%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Frontier at 81.5% to Southwest at 69.4%. One 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 DEN to SJC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Frontier Airlinesthin sample	54	81.5%	36 min	0.00%	B+
United Airlines	996	80.5%	72 min	0.00%	B+
Southwest Airlines (this page)	1,529	69.4%	52 min	0.65%	C+

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 35 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–8am87 flights86.2%
8am–11am373 flights88.4%
11am–2pm262 flights70.9%
2pm–5pm259 flights65.6%
5pm–8pm244 flights55.6%
8pm–5am304 flights53.8%

Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 53.8% on time, against 88.4% for the 8am–11am 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 373 flights scheduled in it.

Across the year

Southwest on DEN to SJC through the year

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

June is the worst month at 45.7% on time, 43 points below November, the best at 88.7%. 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 151 flights.

Across the week, Wednesday is the strongest day at 77.3% on time and Monday the weakest at 62.7%. 15 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 56% of the 24,000 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
56%
Carrier
35%
National Airspace System
9%
Extreme weather
0%
Security
0%

56% 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 24,000 reported delay minutes here, that single category outweighs weather by 56 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 24,257 reported delay minutes.

The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 8,485 of the 24,000 delay minutes reported here.

Cancellations are rare at 0.65%, 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

8.6% 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 roughly 50 minutes, which a normal layover absorbs.

The 948 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 76.3% on time across 1,527 flights, 7 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 7 points of difference.

The sample behind these figures is 1,529 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 DEN to SJC

Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 88.7% on time and June 45.7%, a swing of 43 points. If the dates move at all, move them out of June before you think about anything else. 1,519 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