Route reliability record
SFO→DEN
San Francisco to Denver
- Flights
- 5,410
- Period
- July 2025 to June 2026
- Distance
- 967 mi
- Carriers
- 3
This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 5,410 flights, of which United Airlines flew 3,370 at 82.2% on time.
United Airlines is the most reliable of the three carriers covered here at 82.2% on time across 3,370 flights.
Key figures
On time
75.5%
Arrivals under 15 minutes late, of 5,365 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
0.46%
National rate is 1.81%
Best carrier
United
82.2% on time across 3,370 flights
These figures cover 5,410 flights between July 2025 and June 2026. The median arrival is 4 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 SFO to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 82.2% of the time; Southwest Airlines manages 60.5%. Sample sizes sit next to every figure, because a two-point gap across 1,436 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,370 | 82.2% | 59 min | 0.27% | B+ |
| Frontier Airlines | 604 | 73.2% | 61 min | 0.99% | C+ |
| Southwest Airlines | 1,436 | 60.5% | 58 min | 0.70% | D+ |
The spread between United and Southwest is 22 points, wide enough that it should decide the booking. On a hundred trips that is 22 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 31 points, against 22 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,451 flights92.6%
- 8am–11am805 flights76.9%
- 11am–2pm1,051 flights62.0%
- 2pm–5pm1,074 flights62.6%
- 5pm–8pm558 flights76.4%
- 8pm–5am471 flights78.1%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 62.0% on time against 92.6% 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 1,451 flights scheduled in it.
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. June was the busiest month here, with 494 flights.
Across the week, Saturday is the strongest day at 80.0% on time and Thursday the weakest at 71.9%. 8 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 49% of the 77,000 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.
- 49%Late-arriving aircraft
- 26%Carrier
- 24%National Airspace System
- 1%Extreme weather
49% 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 77,000 reported delay minutes here, that single category outweighs weather by 49 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 77,016 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 92.6% on time here.
Cancellations are rare at 0.46%, 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
7.8% 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 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 65.8% on time across 5,415 flights, 10 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 10 points of difference.
The sample behind these figures is 5,410 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 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. 5,365 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 arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.5% of the 5,410 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SFO to DEN?
United Airlines leads at 82.2% on time across 3,370 flights. Southwest Airlines is at the other end on 60.5%, a gap of 22 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 92.6% on time. The 11am–2pm window is the weakest at 62.0%, 31 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-time record82.2%
- Frontier Airlines on-time record73.2%
- Southwest Airlines on-time record60.5%
- 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. 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.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.