Carrier route record
UAIAH→MIA
United Airlines · Houston to Miami
- Flights
- 1,479
- Period
- July 2025 to June 2026
- Share of route
- 40%
- Carriers
- 6
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on IAH to MIA lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,479 flights. The strongest carrier on the route with a full sample, American Airlines, flew 1,526 at 78.3% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on IAH 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
80.3%
Arrivals under 15 minutes late, of 1,469 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.41%
National rate is 1.81%
Whole route
77.8%
Every carrier on IAH to MIA, 3,736 flights
These figures cover 1,479 flights between July 2025 and June 2026. The median arrival is 8 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
United against every carrier on IAH to MIA
United flew 1,479 of the 3,736 flights on IAH to MIA, about 40% of it. Its 80.3% on time is 3 points better than the route as a whole, which runs 77.8%. Ranked by on-time rate it is first of six carriers on the route, where the range runs from United at 80.3% to Republic at 64.3%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. American Airlines arrives on time 78.3% of the time; Spirit Airlines manages 70.7%. Sample sizes sit next to every figure, because a two-point gap across 441 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 1,479 | 80.3% | 61 min | 0.41% | B+ |
| Envoy Airthin sample | 122 | 78.5% | 52 min | 0.00% | B+ |
| American Airlines | 1,526 | 78.3% | 111 min | 1.31% | B |
| Spirit Airlines | 441 | 70.7% | 79 min | 3.17% | C− |
| Frontier Airlinesthin sample | 154 | 68.9% | 142 min | 1.95% | C |
| Republic Airwaysthin sample | 14 | 64.3% | 173 min | 0.00% | D+ |
Spirit Airlines cancels 3.2% 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.
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am332 flights89.1%
- 8am–11am109 flights80.7%
- 11am–2pm365 flights82.2%
- 2pm–5pm248 flights74.6%
- 5pm–8pm423 flights74.8%
- 8pm–5am2 flights—
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.1% of the time, against 74.6% for the afternoon window. That is 15 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 423 flights scheduled in it.
Across the year
United on IAH to MIA through the year
July is the worst month at 60.5% on time, 29 points below November, the best at 89.1%. 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 146 flights.
Across the week, Tuesday is the strongest day at 87.1% on time and Saturday the weakest at 75.0%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United 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 18,000 reported delay minutes.
- 33%Late-arriving aircraft
- 30%National Airspace System
- 26%Carrier
- 11%Extreme weather
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 89.1% on time here. The split is drawn from 17,660 reported delay minutes.
No single cause dominates. late-arriving aircraft at 33%, national airspace system at 30% and carrier at 26% split the 18,000 reported delay minutes between them. An even spread like this usually means the operation is running close to its designed capacity with no one obvious weak point, and it is the hardest pattern for a traveller to route around.
Cancellations are rare at 0.41%, 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 costs
6.3% 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 last about an hour, which a normal layover absorbs.
The 964 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 85.9% on time across 1,479 flights, 6 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 6 points of difference.
The sample behind these figures is 1,479 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 United on IAH to MIA
Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 89.1% on time and July 60.5%, a swing of 29 points. If the dates move at all, move them out of July before you think about anything else. 1,469 completed flights over 12 months sit behind that.
Related
Where to go next
- IAH to MIA, every carrier
- United on MIA to IAH, the return leg
- Envoy Air on IAH to MIA78.5%
- American Airlines on IAH to MIA78.3%
- Spirit Airlines on IAH to MIA70.7%
- Frontier Airlines on IAH to MIA68.9%
- United Airlines network-wide record
- George Bush Intercontinental (IAH) 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.