Carrier route record
F9DEN→MIA
Frontier Airlines · Denver to Miami
- Flights
- 353
- Period
- September 2025 to August 2026
- Share of route
- 14%
- Carriers
- 4
Historical statistics for September 2025 to August 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, 3 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 353 flights. The strongest carrier on the route with a full sample, American Airlines, flew 890 at 77.8% on time.
The US average over the same twelve months is 77.3%, so there is little to separate Frontier on DEN to MIA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
73.9%
Arrivals under 15 minutes late, of 352 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.28%
National rate is 1.89%
Whole route
74.9%
Every carrier on DEN to MIA, 2,443 flights
These figures cover 353 flights between September 2025 and August 2026. The median arrival is 5 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.
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Carrier by carrier
Frontier against every carrier on DEN to MIA
Frontier flew 353 of the 2,443 flights on DEN to MIA, about 14% of it. Its 73.9% on time is about level with the route as a whole at 74.9%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from American at 77.8% to Southwest at 64.5%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 2 points 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 | 890 | 77.8% | 96 min | 1.01% | B |
| United Airlines | 877 | 76.3% | 60 min | 0.00% | B+ |
| Frontier Airlines (this page)thin sample | 353 | 73.9% | 63 min | 0.28% | C+ |
| Southwest Airlinesthin sample | 323 | 64.5% | 48 min | 0.62% | D+ |
No carrier stands out. American tops the table at 77.8%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Frontier flight numbers on DEN to MIA
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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 2 points between the best and worst carrier.
- 5am–8am4 flights—
- 8am–11am11 flights—
- 11am–2pm22 flights—
- 2pm–5pm1 flights—
- 5pm–8pm30 flights60.0%
- 8pm–5am285 flights77.8%
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 77.8% 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 285 flights scheduled in it.
Across the year
Frontier on DEN to MIA through the year
- Jul–Sep 202520 flights—
- Oct–Dec 202580 flights73.8%
- Jan–Mar 2026101 flights69.0%
- Apr–Jun 202690 flights85.6%
- Jul–Sep 202662 flights66.1%
Scale runs 60% 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 73.9% on time across 353 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 2026 at 66.1%, a swing of 20 points on roughly 88 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 88.5% on time and Friday the weakest at 60.7%, a spread of 28 points.
Arrival by arrival
How late Frontier on DEN to MIA runs when it is late
Frontier on DEN to MIA often beats the schedule: 116 of 352 completed flights, 33%, arrived 15 minutes or more early. The 92 late arrivals split 31 under half an hour, 34 between 30 and 60 minutes, and 27 an hour or more.
- 15+ min early116 flights33.0%
- Within 15 min144 flights40.9%
- 15–29 min late31 flights8.8%
- 30–59 min late34 flights9.7%
- 1–2 hours late17 flights4.8%
- 2+ hours late10 flights2.8%
Scale runs 0% to 100%.
Share of 352 completed flights by arrival against schedule.
17 of 92 late departures made up the time and arrived on time, 18% of them. 17 flights left on time and still arrived late.
The worst days
Worst days for Frontier on DEN to MIA
The latest arrival of the period was on 1 December 2025, 7 hours 52 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). Three of the five worst days fell in March 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 1 December 2025 | 7 hours 52 minutes | Carrier |
| 16 March 2026 | 5 hours 16 minutes | Late-arriving aircraft |
| 23 March 2026 | 3 hours 58 minutes | Late-arriving aircraft |
| 19 May 2026 | 3 hours 54 minutes | Carrier |
| 6 March 2026 | 3 hours 33 minutes | Late-arriving aircraft |
Delay causes
Why Frontier runs late on this route
Carrier accounts for 44% of the 5,768 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Carrier
- 35%Late-arriving aircraft
- 19%National Airspace System
- 3%Extreme weather
35% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,768 reported delay minutes here, that single category outweighs weather by 13 to one. The split is drawn from 5,768 reported delay minutes.
The largest share of delay minutes, 44%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,546 of the 5,768 delay minutes reported here.
Cancellations are rare at 0.28%, 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 costs
7.7% of arrivals land an hour or more late, close to the national 8.3%, so 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 83.2% on time across 355 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. 353 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. 353 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 73.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 352 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 MIA77.8%
- United Airlines on DEN to MIA76.3%
- Southwest Airlines on DEN to MIA64.5%
- 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 7.05 million flight records
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.