Carrier route record
WNMIA→DEN
Southwest Airlines · Miami to Denver
- Flights
- 323
- Period
- September 2025 to August 2026
- Share of route
- 13%
- Carriers
- 4
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on MIA to DEN earns an F+, which is as low as this site's scale goes for a reason. Only 54.5% of flights arrive inside the 15-minute window, 23 points worse than the national rate of 77.3%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 323 flights. The strongest carrier on the route with a full sample, United Airlines, flew 877 at 83.0% on time.
The national on-time rate over the same period is 77.3%, so Southwest on MIA to DEN runs 23 points behind the country as a whole. Across a thousand flights that is about 228 extra late arrivals.
Key figures
On time
54.5%
Arrivals under 15 minutes late, of 319 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
Whole route
76.8%
Every carrier on MIA to DEN, 2,444 flights
These figures cover 323 flights between September 2025 and August 2026. Beyond the headline rate, 16.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on MIA to DEN
Southwest flew 323 of the 2,444 flights on MIA to DEN, about 13% of it. Its 54.5% on time is 22 points worse than the route as a whole, which runs 76.8%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from Frontier at 83.2% to Southwest at 54.5%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. United Airlines arrives on time 83.0% of the time; American Airlines manages 76.1%. Sample sizes sit next to every figure, because a two-point gap across 889 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlinesthin sample | 355 | 83.2% | 91 min | 0.85% | B+ |
| United Airlines | 877 | 83.0% | 73 min | 0.11% | B+ |
| American Airlines | 889 | 76.1% | 58 min | 0.90% | B+ |
| Southwest Airlines (this page)thin sample | 323 | 54.5% | 61 min | 0.00% | F+ |
United leads American by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 7 points between the best and worst carrier.
- 5am–8am22 flights—
- 8am–11am15 flights—
- 11am–2pm52 flights58.8%
- 2pm–5pm199 flights47.4%
- 5pm–8pm35 flights45.7%
- 8pm–5am—
Scale runs 35% to 65%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 45.7% on time, against 58.8% for the 11am–2pm 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 2pm–5pm window is the busiest, with 199 flights scheduled in it.
Across the year
Southwest on MIA to DEN through the year
- Jul–Sep 202517 flights—
- Oct–Dec 202587 flights60.5%
- Jan–Mar 202695 flights72.6%
- Apr–Jun 202674 flights45.1%
- Jul–Sep 202650 flights24.0%
Scale runs 15% to 80%. 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 54.5% on time across 323 flights.
Southwest on MIA to DEN did not run the same all year. Its best quarter was Jan–Mar 2026 at 72.6% on time and its weakest Jul–Sep 2026 at 24.0%, a swing of 49 points on roughly 81 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, Sunday is the strongest day at 56.9% on time and Thursday the weakest at 47.1%, a spread of 10 points.
Arrival by arrival
How late Southwest on MIA to DEN runs when it is late
The 145 late arrivals split 49 under half an hour, 43 between 30 and 60 minutes, and 53 an hour or more.
- 15+ min early27 flights8.5%
- Within 15 min147 flights46.1%
- 15–29 min late49 flights15.4%
- 30–59 min late43 flights13.5%
- 1–2 hours late36 flights11.3%
- 2+ hours late17 flights5.3%
Scale runs 0% to 100%.
Share of 319 completed flights by arrival against schedule.
40 of 162 late departures made up the time and arrived on time, 25% of them. In the other direction, 23 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at DEN.
The worst days
Worst days for Southwest on MIA to DEN
The latest arrival of the period was on 27 July 2026, 5 hours 51 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in July 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 27 July 2026 | 5 hours 51 minutes | Late-arriving aircraft |
| 1 July 2026 | 4 hours 45 minutes | Late-arriving aircraft |
| 7 March 2026 | 4 hours 3 minutes | Carrier |
| 28 July 2026 | 3 hours 38 minutes | National Airspace System |
| 30 April 2026 | 3 hours 18 minutes | National Airspace System |
Delay causes
Why Southwest runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 8,766 reported delay minutes.
- 40%Late-arriving aircraft
- 31%National Airspace System
- 25%Carrier
- 5%Extreme weather
40% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 8,766 reported delay minutes here, that single category outweighs weather by 8 to one. The split is drawn from 8,766 reported delay minutes.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
16.6% 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.
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 64.5% on time across 323 flights, 10 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 10 points of difference.
One caution: this is a thin sample. 323 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 Southwest on MIA to DEN
Put together: treat all of this as provisional. 323 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 54.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 319 completed flights over 12 months sit behind that.
Related
Where to go next
- MIA to DEN, every carrier
- Southwest on DEN to MIA, the return leg
- Frontier Airlines on MIA to DEN83.2%
- United Airlines on MIA to DEN83.0%
- American Airlines on MIA to DEN76.1%
- Southwest Airlines network-wide record
- Miami International (MIA) delay statistics
- Denver International (DEN) 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.