Route reliability record
SFO→DEN
San Francisco to Denver
- Flights
- 5,486
- Period
- September 2025 to August 2026
- Distance
- 967 mi
- Carriers
- 3
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, 3 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 5,486 SFO to DEN flights, of which United Airlines flew 3,427 at 82.1% on time.
Best time to fly SFO to DEN: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 93.8% of the time and Saturday flights 79.7%, against 74.7% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 82.1% on time across 3,427 flights.
Key figures
On time
74.7%
Arrivals under 15 minutes late, of 5,435 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.46%
National rate is 1.89%
Best carrier
United
82.1% on time across 3,427 flights
These figures cover 5,486 flights between September 2025 and August 2026. Beyond the headline rate, 9.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on SFO to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 82.1% of the time; Southwest Airlines manages 59.0%. Sample sizes sit next to every figure, because a two-point gap across 1,391 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,427 | 82.1% | 58 min | 0.18% | B+ |
| Frontier Airlines | 668 | 68.9% | 68 min | 1.20% | C |
| Southwest Airlines | 1,391 | 59.0% | 62 min | 0.79% | D+ |
The spread between United and Southwest is 23 points, wide enough that it should decide the booking. On a hundred trips that is 23 more arrivals inside the on-time window.
Flight by flight
Flights on SFO to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly San Francisco to Denver
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJC → DENSan Jose to Denver | United Airlines | 89.0% | 89.3% | 0.30% | 8am–11am, Sat | — |
| 2. SFO → DENSan Francisco to Denver | United Airlines | 82.0% | 82.1% | 0.18% | 5am–8am, Sat | UA 2348 08:35 |
| 3. SJC → DENSan Jose to Denver | Southwest Airlines | 74.5% | 74.8% | 0.46% | 5am–8am, Tue | — |
| 4. OAK → DENOakland to Denver | Southwest Airlines | 71.1% | 71.4% | 0.37% | 5am–8am, Sat | — |
| 5. SFO → DENSan Francisco to Denver | Frontier Airlines | 68.1% | 68.9% | 1.20% | 8am–11am, Wed | F9 1230 06:00 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 33 points, against 23 points between the best and worst carrier.
- 5am–8am1,443 flights93.8%
- 8am–11am833 flights73.0%
- 11am–2pm995 flights61.2%
- 2pm–5pm1,025 flights61.2%
- 5pm–8pm629 flights74.6%
- 8pm–5am561 flights76.4%
Scale runs 55% to 100%.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 61.2% on time against 93.8% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 5am–8am window is the busiest, with 1,443 flights scheduled in it.
Explore
Filter SFO to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On SFO to DEN, the best departure window is 5am–8am at 93.8% on time and the worst is 11am–2pm at 61.2%, a wide gap of 32.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am93.8%
- 8–11am73.0%
- 11am–2pm61.2%
- 2–5pm61.2%
- 5–8pm74.6%
- 8pm–5am76.4%
best all US flightsScale 55% to 100%.
Across the year
When delays peak on this route
This route's year swings by 24 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 63.7% on time, 24 points below January, the best at 87.3%. 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 514 flights.
Across the week, Saturday is the strongest day at 79.7% on time and Thursday the weakest at 71.4%, a spread of 8 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 55% of the 84,000 delay minutes carriers reported here, and the remaining four split what is left.
- 55%Late-arriving aircraft
- 24%Carrier
- 22%National Airspace System
- 0%Extreme weather
- 0%Security
55% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 84,000 reported delay minutes here, that single category outweighs weather by 55 to one. The split is drawn from 84,161 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 93.8% on time here.
Cancellations are rare at 0.46%, below the national 1.89% 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
9.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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.
The return leg is a different operation and performs like one: it runs 63.2% on time across 5,488 flights, 12 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 12 points of difference.
The sample behind these figures is 5,486 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.
Work out the risk of missing a connection in DEN after this flight
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 87.3% on time and June 63.7%, a swing of 24 points. If the dates move at all, move them out of June before you think about anything else. 5,435 completed flights over 12 months sit behind that.
Common questions
SFO to DEN questions
How often is SFO to DEN delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 25.3% of the 5,486 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SFO to DEN?
United Airlines leads at 82.1% on time across 3,427 flights. Southwest Airlines is at the other end on 59.0%, a gap of 23 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 SFO to DEN?
The 5am–8am departure window is the strongest at 93.8% on time. The 2pm–5pm window is the weakest at 61.2%, 33 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 SFO to DEN?
June is the weakest month at 63.7% on time, compared with 87.3% in January. Across the year that is 24 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 SFO — the return legseparate record
- San Francisco International (SFO) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on SFO to DEN82.1%
- Frontier Airlines on SFO to DEN68.9%
- Southwest Airlines on SFO to DEN59.0%
- SFO to LAX, a related route70.9%
- PHX to DEN, a related route76.7%
- SFO to SEA, a related route72.3%
- United Airlines on-time record82.1%
- Frontier Airlines on-time record68.9%
- Southwest Airlines on-time record59.0%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. SFO to DEN and DEN to SFO are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.