Route reliability record
MIA→DEN
Miami to Denver
- Flights
- 2,491
- Period
- July 2025 to June 2026
- Distance
- 1,709 mi
- Carriers
- 4
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 2,491 flights, of which United Airlines flew 932 at 82.1% on time.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
77.1%
Arrivals under 15 minutes late, of 2,458 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
0.52%
National rate is 1.81%
Best carrier
United
82.1% on time across 932 flights
These figures cover 2,491 flights between July 2025 and June 2026. The median arrival is 7 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 MIA to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 82.1% of the time; American Airlines manages 75.7%. Sample sizes sit next to every figure, because a two-point gap across 885 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlinesthin sample | 351 | 82.8% | 112 min | 1.42% | B |
| United Airlines | 932 | 82.1% | 68 min | 0.11% | B+ |
| American Airlines | 885 | 75.7% | 63 min | 0.79% | B+ |
| Southwest Airlinesthin sample | 323 | 59.7% | 57 min | 0.00% | D+ |
United leads American by 6 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 23 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am543 flights89.0%
- 8am–11am537 flights87.3%
- 11am–2pm216 flights76.4%
- 2pm–5pm557 flights66.3%
- 5pm–8pm243 flights69.0%
- 8pm–5am395 flights67.0%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.0% of the time, against 66.3% for the afternoon window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 557 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 14 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.
August is the worst month at 69.7% on time, 14 points below February, the best at 83.6%. 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. March was the busiest month here, with 281 flights.
Across the week, Tuesday is the strongest day at 80.9% on time and Sunday the weakest at 73.2%. 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 43% of the 38,000 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.
- 43%Late-arriving aircraft
- 31%Carrier
- 22%National Airspace System
- 4%Extreme weather
- 1%Security
43% 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 38,000 reported delay minutes here, that single category outweighs weather by 11 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 38,420 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 89.0% on time here.
Cancellations are rare at 0.52%, 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
7.3% 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 a little over an hour kind, 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 74.0% on time across 2,490 flights, 3 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 3 points of difference.
The sample behind these figures is 2,491 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. February runs 83.6% on time and August 69.7%, a swing of 14 points. If the dates move at all, move them out of August before you think about anything else. 2,458 completed flights over 12 months sit behind that.
Common questions
MIA to DEN questions
How often is MIA to DEN delayed?
Roughly 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 22.9% of the 2,491 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on MIA to DEN?
United Airlines leads at 82.1% on time across 932 flights. American Airlines is at the other end on 75.7%, a gap of 6 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 MIA to DEN?
The 5am–8am departure window is the strongest at 89.0% on time. The 2pm–5pm window is the weakest at 66.3%, 23 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 August delays on MIA to DEN?
August is the weakest month at 69.7% on time, compared with 83.6% in February. Across the year that is 14 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 MIA — the return legseparate record
- Miami International (MIA) delay statistics
- Denver International (DEN) delay statistics
- Frontier Airlines on-time record82.8%
- United Airlines on-time record82.1%
- American Airlines on-time record75.7%
- 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. MIA to DEN and DEN to MIA 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.