Route reliability record
DEN→SFO
Denver to San Francisco
- Flights
- 5,391
- Period
- June 2025 to May 2026
- Distance
- 967 mi
- Carriers
- 3
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, 9 points worse than the national rate of 77.4%. The late ones land about an hour behind schedule. That rests on 5,391 flights, of which United Airlines flew 3,367 at 73.0% on time.
United Airlines is the most reliable of the three carriers covered here at 73.0% on time across 3,367 flights.
Key figures
On time
68.1%
Arrivals under 15 minutes late, of 5,359 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.54%
National rate is 1.80%
Best carrier
United
73.0% on time across 3,367 flights
These figures cover 5,391 flights between June 2025 and May 2026. Beyond the headline rate, 11.3% 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
Which airline is most reliable on DEN to SFO
The choice of carrier is not cosmetic here. United Airlines arrives on time 73.0% of the time; Southwest Airlines manages 55.7%. Sample sizes sit next to every figure, because a two-point gap across 1,459 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,367 | 73.0% | 65 min | 0.45% | C+ |
| Frontier Airlines | 565 | 71.2% | 59 min | 0.88% | C+ |
| Southwest Airlines | 1,459 | 55.7% | 57 min | 0.62% | D+ |
The spread between United and Southwest is 17 points, wide enough that it should decide the booking. On a hundred trips that is 17 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 28 points, against 17 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am735 flights85.3%
- 8am–11am861 flights69.0%
- 11am–2pm1,011 flights73.3%
- 2pm–5pm619 flights71.9%
- 5pm–8pm1,006 flights57.8%
- 8pm–5am1,159 flights59.0%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 57.8% on time, against 85.3% 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 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.
Delays peak in May, when the on-time rate falls to 53.5%. March is the strongest month at 82.2%. Moving a flexible trip across that boundary buys 29 points.
Across the week, Saturday is the strongest day at 75.3% on time and Thursday the weakest at 61.3%. 14 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 104,000 reported delay minutes.
- 39%National Airspace System
- 38%Late-arriving aircraft
- 22%Carrier
- 2%Extreme weather
38% 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 104,000 reported delay minutes here, that single category outweighs weather by 24 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.
39% 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 40,000 minutes out of 104,000, against a national NAS share of 21%.
Cancellations are rare at 0.54%, below the national 1.80% 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.3% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 967 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 76.0% on time across 5,384 flights, 8 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 8 points of difference.
The sample behind these figures is 5,391 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. March runs 82.2% on time and May 53.5%, a swing of 29 points. If the dates move at all, move them out of May before you think about anything else.
Common questions
DEN to SFO questions
How often is DEN to SFO delayed?
About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 31.9% of the 5,391 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DEN to SFO?
United Airlines leads at 73.0% on time across 3,367 flights. Southwest Airlines is at the other end on 55.7%, a gap of 17 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 DEN to SFO?
The 5am–8am departure window is the strongest at 85.3% on time. The 5pm–8pm window is the weakest at 57.8%, 28 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 May delays on DEN to SFO?
May is the weakest month at 53.5% on time, compared with 82.2% in March. 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
- SFO to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- San Francisco International (SFO) delay statistics
- United Airlines on-time record73.0%
- Frontier Airlines on-time record71.2%
- Southwest Airlines on-time record55.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. DEN to SFO and SFO to DEN 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.