Carrier performance at one airport
UA→MIA
United Airlines at Miami International
- Departures
- 6,839
- Period
- July 2025 to June 2026
- Routes
- 6
- Rank here
- #2 of 9
United Airlines at Miami lands a B, level with the national rate of 77.6%. Roughly one flight in five arrive 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 6,839 flights, of which Envoy Air flew 13,859 at 83.1% on time.
Measured against the airport rather than the country, United Airlines runs 4 points ahead of the 73.8% weighted average across all carriers at MIA. That is the comparison worth making: every operator here works the same runways, the same airspace and the same weather.
Key figures
On time
77.9%
6,743 completed departures
Avg delay
83 min
Across delayed flights only
Cancelled
1.01%
At MIA, this carrier only
Rank here
#2
Of 9 carriers clearing the floor at MIA
These figures cover 6,839 flights between July 2025 and June 2026. Beyond the headline rate, 9.2% 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.
Against the competition
Every carrier at MIA, ranked
The choice of carrier is not cosmetic here. Envoy Air arrives on time 83.1% of the time; Spirit Airlines manages 65.8%. Sample sizes sit next to every figure, because a two-point gap across 3,516 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Air | 13,859 | 83.1% | 48 min | 0.84% | B+ |
| United Airlines (this page) | 6,839 | 77.9% | 83 min | 1.01% | B |
| Frontier Airlines | 4,274 | 75.1% | 86 min | 2.20% | B |
| Delta Air Lines | 11,625 | 74.1% | 78 min | 2.10% | C |
| American Airlines | 63,941 | 71.9% | 73 min | 1.61% | C |
| Southwest Airlines | 5,316 | 71.6% | 59 min | 1.13% | C |
| Alaska Airlines | 533 | 69.6% | 56 min | 1.50% | C |
| Republic Airways | 1,069 | 68.6% | 86 min | 1.31% | C |
| Spirit Airlines | 3,516 | 65.8% | 78 min | 4.64% | C− |
Spirit Airlines cancels 4.6% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Route by route
Where United Airlines flies from MIA
United Airlines operates 6 routes out of MIA with enough volume to report. Route records inside one carrier at one airport still spread widely, because a short shuttle and a transcontinental have very different exposure to a late inbound.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| MIA to EWR · Newark | 2,253 | 74.9% | 88 min | 2.04% | C |
| MIA to IAH · Houston | 1,479 | 85.9% | 91 min | 0.61% | A+ |
| MIA to ORD · Chicago | 1,040 | 70.7% | 85 min | 0.87% | C+ |
| MIA to DEN · Denver | 932 | 82.1% | 68 min | 0.11% | B+ |
| MIA to SFO · San Francisco | 623 | 72.2% | 71 min | 0.32% | C+ |
| MIA to IAD · Washington | 512 | 82.5% | 79 min | 0.39% | B+ |
Departure window
Best time of day for this operation
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 30 points, against 17 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,233 flights92.0%
- 8am–11am1,026 flights89.5%
- 11am–2pm1,738 flights82.8%
- 2pm–5pm1,240 flights67.2%
- 5pm–8pm1,380 flights62.0%
- 8pm–5am222 flights65.1%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 62.0% on time, against 92.0% for the 5am–8am 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 11am–2pm window is the busiest, with 1,738 flights scheduled in it.
Across the year
Seasonal pattern
August is the worst month at 69.2% on time, 17 points below April, the best at 85.7%. 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 764 flights.
Delay causes
What holds this operation up
- 39%National Airspace System
- 32%Late-arriving aircraft
- 24%Carrier
- 5%Extreme weather
- 0%Security
39% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 48,000 minutes out of 123,000, against a national NAS share of 21%. The split is drawn from 123,311 reported delay minutes.
Cancellations sit at 1.01% against a national 1.81%, which is ordinary. Diversions add another 0.39%.
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.2% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The sample behind these figures is 6,839 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.
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 85.7% on time and August 69.2%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 6,743 completed flights over 12 months sit behind that.
Common questions
United Airlines at MIA
How often is United Airlines at MIA delayed?
Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.1% of the 6,839 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on United Airlines at MIA?
Envoy Air leads at 83.1% on time across 13,859 flights. Spirit Airlines is at the other end on 65.8%, a gap of 17 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 United Airlines at MIA?
The 5am–8am departure window is the strongest at 92.0% on time. The 5pm–8pm window is the weakest at 62.0%, 30 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 United Airlines at MIA?
August is the weakest month at 69.2% on time, compared with 85.7% in April. Across the year that is 17 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
- United Airlines network-wide record
- Miami International (MIA) all carriers
- MIA to EWR route record74.9%
- MIA to IAH route record85.9%
- MIA to ORD route record70.7%
- MIA to DEN route record82.1%
- 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. Updated monthly. How this data is collected.