Route reliability record
SJC→DEN
San Jose to Denver
- Flights
- 2,579
- Period
- July 2025 to June 2026
- Distance
- 948 mi
- Carriers
- 3
This route lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 2,579 flights, of which United Airlines flew 998 at 88.3% on time.
The US average over the same twelve months is 77.6%, 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.
Key figures
On time
81.0%
Arrivals under 15 minutes late, of 2,561 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.43%
National rate is 1.81%
Best carrier
United
88.3% on time across 998 flights
These figures cover 2,579 flights between July 2025 and June 2026. The median arrival is 6 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
Which airline is most reliable on SJC to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 88.3% of the time; Southwest Airlines manages 76.3%. Sample sizes sit next to every figure, because a two-point gap across 1,527 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 998 | 88.3% | 68 min | 0.40% | A+ |
| Frontier Airlinesthin sample | 54 | 81.5% | 45 min | 0.00% | B+ |
| Southwest Airlines | 1,527 | 76.3% | 52 min | 0.46% | B+ |
The spread between United and Southwest is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 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 27 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am394 flights95.1%
- 8am–11am632 flights92.4%
- 11am–2pm435 flights78.5%
- 2pm–5pm744 flights68.5%
- 5pm–8pm333 flights75.2%
- 8pm–5am41 flights73.2%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 95.1% of the time, against 68.5% for the afternoon window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 744 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 29 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.
June is the worst month at 64.1% on time, 29 points below January, the best at 93.1%. 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. September was the busiest month here, with 264 flights.
Across the week, Saturday is the strongest day at 87.3% on time and Thursday the weakest at 75.4%. 12 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 27,000 reported delay minutes.
- 38%National Airspace System
- 34%Late-arriving aircraft
- 26%Carrier
- 2%Extreme weather
- 1%Security
34% 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 27,000 reported delay minutes here, that single category outweighs weather by 20 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 27,200 reported delay minutes.
38% 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 10,000 minutes out of 27,000, against a national NAS share of 21%.
Cancellations are rare at 0.43%, 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 actually costs
5.7% 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 about an hour kind, 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 74.0% on time across 2,579 flights, 7 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 7 points of difference.
The sample behind these figures is 2,579 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 93.1% on time and June 64.1%, a swing of 29 points. If the dates move at all, move them out of June before you think about anything else. 2,561 completed flights over 12 months sit behind that.
Common questions
SJC to DEN questions
How often is SJC to DEN delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.0% of the 2,579 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SJC to DEN?
United Airlines leads at 88.3% on time across 998 flights. Southwest Airlines is at the other end on 76.3%, a gap of 12 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 DEN?
The 5am–8am departure window is the strongest at 95.1% on time. The 2pm–5pm window is the weakest at 68.5%, 27 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 DEN?
June is the weakest month at 64.1% on time, compared with 93.1% in January. Across the year that is 29 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to SJC — the return legseparate record
- Norman Y. Mineta San Jose International (SJC) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on-time record88.3%
- Frontier Airlines on-time record81.5%
- Southwest Airlines on-time record76.3%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SJC to DEN and DEN 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.