Carrier route record
F9SFO→DEN
Frontier Airlines · San Francisco to Denver
- Flights
- 604
- Period
- July 2025 to June 2026
- Share of route
- 11%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.
Frontier on SFO to DEN sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 604 flights. The strongest carrier on the route with a full sample, United Airlines, flew 3,370 at 82.2% on time.
The national on-time rate over the same period is 77.6%, so Frontier on SFO to DEN runs 4 points behind the country as a whole. Across a thousand flights that is about 44 extra late arrivals.
Key figures
On time
73.2%
Arrivals under 15 minutes late, of 598 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.99%
National rate is 1.81%
Whole route
75.5%
Every carrier on SFO to DEN, 5,410 flights
These figures cover 604 flights between July 2025 and June 2026. Beyond the headline rate, 8.9% 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
Frontier against every carrier on SFO to DEN
Frontier flew 604 of the 5,410 flights on SFO to DEN, about 11% of it. Its 73.2% on time is 2 points worse than the route as a whole, which runs 75.5%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from United at 82.2% to Southwest at 60.5%.
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 (this page) | 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.
Flight by flight
Frontier flight numbers on SFO to DEN
Departure window
When Frontier runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 71 points, against 22 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am351 flights86.7%
- 8am–11am58 flights89.7%
- 11am–2pm80 flights19.2%
- 2pm–5pm35 flights62.9%
- 5pm–8pm17 flights—
- 8pm–5am63 flights55.6%
Scale runs 10% to 95%. 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 19.2% on time against 89.7% for 8am–11am. 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 351 flights scheduled in it.
Across the year
Frontier on SFO to DEN through the year
June is the worst month at 50.0% on time, 38 points below February, the best at 87.8%. 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 80 flights.
Across the week, Saturday is the strongest day at 78.2% on time and Thursday the weakest at 69.5%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Frontier runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 56% of the 9,693 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.
- 56%Late-arriving aircraft
- 28%Carrier
- 15%National Airspace System
- 0%Extreme weather
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 9,693 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 9,693 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.7% on time here.
Cancellations sit at 0.99% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
8.9% 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 about an hour, 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 67.2% on time across 604 flights, 6 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 6 points of difference.
One caution: this is a thin sample. 604 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Frontier on SFO to DEN
Put together: treat all of this as provisional. 604 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 73.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 598 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to DEN, every carrier
- Frontier on DEN to SFO, the return leg
- United Airlines on SFO to DEN82.2%
- Southwest Airlines on SFO to DEN60.5%
- Frontier Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Denver International (DEN) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.