Carrier route record
F9DEN→MIA
Frontier Airlines · Denver to Miami
- Flights
- 349
- Period
- July 2025 to June 2026
- Share of route
- 14%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.
Frontier on DEN to MIA 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 349 flights. The strongest carrier on the route with a full sample, American Airlines, flew 886 at 76.6% on time.
The national on-time rate over the same period is 77.6%, so Frontier on DEN to MIA runs 4 points behind the country as a whole. Across a thousand flights that is about 40 extra late arrivals.
Key figures
On time
73.6%
Arrivals under 15 minutes late, of 345 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
1.15%
National rate is 1.81%
Whole route
74.0%
Every carrier on DEN to MIA, 2,490 flights
These figures cover 349 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
Frontier against every carrier on DEN to MIA
Frontier flew 349 of the 2,490 flights on DEN to MIA, about 14% of it. Its 73.6% on time is about level with the route as a whole at 74.0%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from American at 76.6% to Southwest at 63.2%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 886 | 76.6% | 102 min | 1.02% | B |
| United Airlines | 932 | 75.4% | 64 min | 0.11% | B+ |
| Frontier Airlines (this page)thin sample | 349 | 73.6% | 59 min | 1.15% | C |
| Southwest Airlinesthin sample | 323 | 63.2% | 51 min | 0.62% | D+ |
No carrier stands out. American tops the table at 76.6%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.
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 18 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am4 flights—
- 8am–11am11 flights—
- 11am–2pm22 flights—
- 2pm–5pm1 flights—
- 5pm–8pm30 flights60.0%
- 8pm–5am281 flights77.6%
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 60.0% on time, against 77.6% for the 8pm–5am 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. The 8pm–5am window is the busiest, with 281 flights scheduled in it.
Across the year
Frontier on DEN to MIA through the year
- Jul–Sep 202578 flights65.3%
- Oct–Dec 202580 flights73.8%
- Jan–Mar 2026101 flights69.0%
- Apr–Jun 202690 flights85.6%
Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 73.6% on time across 349 flights.
Frontier on DEN to MIA did not run the same all year. Its best quarter was Apr–Jun 2026 at 85.6% on time and its weakest Jul–Sep 2025 at 65.3%, a swing of 20 points on roughly 87 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Thursday is the strongest day at 86.5% on time and Friday the weakest at 63.0%. 24 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. Carrier accounts for 44% of the 5,408 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.
- 44%Carrier
- 33%Late-arriving aircraft
- 19%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 44%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,377 of the 5,408 delay minutes reported here. The split is drawn from 5,408 reported delay minutes.
Cancellations sit at 1.15% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
6.7% 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 last about an hour, which a normal layover absorbs.
At 1,709 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 82.8% on time across 351 flights, 9 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 9 points of difference.
One caution: this is a thin sample. 349 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 DEN to MIA
Put together: treat all of this as provisional. 349 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 73.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 345 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to MIA, every carrier
- Frontier on MIA to DEN, the return leg
- American Airlines on DEN to MIA76.6%
- United Airlines on DEN to MIA75.4%
- Southwest Airlines on DEN to MIA63.2%
- Frontier Airlines network-wide record
- Denver International (DEN) delay statistics
- Miami International (MIA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.