Route reliability record
MIA→IAH
Miami to Houston
- Flights
- 3,667
- Period
- September 2025 to August 2026
- Distance
- 964 mi
- Carriers
- 6
This route lands a B, 2 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 3,667 MIA to IAH flights, of which United Airlines flew 1,438 at 87.5% on time.
Best time to fly MIA to IAH: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 91.8% of the time and Tuesday flights 84.5%, against 78.8% for the route overall.
The US average over the same twelve months is 77.3%, 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
78.8%
Arrivals under 15 minutes late, of 3,619 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
1.17%
National rate is 1.89%
Best carrier
United
87.5% on time across 1,438 flights
These figures cover 3,667 flights between September 2025 and August 2026. Beyond the headline rate, 8.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on MIA to IAH
The choice of carrier is not cosmetic here. United Airlines arrives on time 87.5% of the time; American Airlines manages 71.5%. Sample sizes sit next to every figure, because a two-point gap across 1,566 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,438 | 87.5% | 90 min | 0.49% | A+ |
| Envoy Airthin sample | 129 | 86.8% | 39 min | 0.00% | A+ |
| Frontier Airlinesthin sample | 197 | 85.2% | 87 min | 4.06% | A− |
| American Airlines | 1,566 | 71.5% | 69 min | 1.15% | C |
| Spirit Airlinesthin sample | 323 | 68.3% | 86 min | 3.10% | C− |
| Republic Airwaysthin sample | 14 | 64.3% | 133 min | 0.00% | D+ |
The spread between United and American is 16 points, wide enough that it should decide the booking. On a hundred trips that is 16 more arrivals inside the on-time window.
Flight by flight
Flights on MIA to IAH
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Miami to Houston
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. FLL → IAHFort Lauderdale to Houston | United Airlines | 87.7% | 88.3% | 0.63% | 5am–8am, Thu | UA 2314 06:15 |
| 2. MIA → IAHMiami to Houston | United Airlines | 87.1% | 87.5% | 0.49% | 5am–8am, Wed | UA 1216 16:53 |
| 3. MIA → IAHMiami to Houston | American Airlines | 70.7% | 71.5% | 1.15% | 5am–8am, Tue | AA 2230 21:50 |
| 4. FLL → IAHFort Lauderdale to Houston | Spirit Airlines | 70.2% | 71.7% | 2.15% | 5am–8am, Tue | — |
| 5. FLL → HOUFort Lauderdale to Houston | Southwest Airlines | 69.5% | 70.2% | 0.99% | 5am–8am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 26 points, against 16 points between the best and worst carrier.
- 5am–8am605 flights91.8%
- 8am–11am665 flights88.5%
- 11am–2pm580 flights86.3%
- 2pm–5pm641 flights68.8%
- 5pm–8pm686 flights69.5%
- 8pm–5am490 flights66.1%
Scale runs 60% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.8% of the time, against 66.1% for the overnight window. That is 26 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 686 flights scheduled in it.
Explore
Filter MIA to IAH by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On MIA to IAH, the best departure window is 5am–8am at 91.8% on time and the worst is 8pm–5am at 66.1%, a wide gap of 25.7 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.8%
- 8–11am88.5%
- 11am–2pm86.3%
- 2–5pm68.8%
- 5–8pm69.5%
- 8pm–5am66.1%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 16 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.
Delays peak in March, when the on-time rate falls to 69.0%. January is the strongest month at 84.7%. Moving a flexible trip across that boundary buys 16 points. January was the busiest month here, with 342 flights.
Across the week, Tuesday is the strongest day at 84.5% on time and Sunday the weakest at 70.1%, a spread of 14 points.
Delay causes
Why this route gets delayed
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 59,000 reported delay minutes.
- 34%Late-arriving aircraft
- 33%Carrier
- 26%National Airspace System
- 7%Extreme weather
- 0%Security
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 91.8% on time here. The split is drawn from 58,890 reported delay minutes.
No single cause dominates. late-arriving aircraft at 34%, carrier at 33% and national airspace system at 26% split the 59,000 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 sit at 1.17% against a national 1.89%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
8.1% 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 a little over 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.
The return leg runs 78.6% on time across 3,665 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 3,667 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.
Work out the risk of missing a connection in IAH after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 84.7% on time and March 69.0%, a swing of 16 points. If the dates move at all, move them out of March before you think about anything else. 3,619 completed flights over 12 months sit behind that.
Common questions
MIA to IAH questions
How often is MIA to IAH delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.2% of the 3,667 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on MIA to IAH?
United Airlines leads at 87.5% on time across 1,438 flights. American Airlines is at the other end on 71.5%, a gap of 16 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 IAH?
The 5am–8am departure window is the strongest at 91.8% on time. The 8pm–5am window is the weakest at 66.1%, 26 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 March delays on MIA to IAH?
March is the weakest month at 69.0% on time, compared with 84.7% in January. Across the year that is 16 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
- IAH to MIA — the return legseparate record
- Miami International (MIA) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on MIA to IAH87.5%
- Envoy Air on MIA to IAH86.8%
- Frontier Airlines on MIA to IAH85.2%
- American Airlines on MIA to IAH71.5%
- Spirit Airlines on MIA to IAH68.3%
- MIA to ATL, a related route74.2%
- ORD to IAH, a related route76.0%
- MIA to LGA, a related route67.4%
- United Airlines on-time record87.5%
- Envoy Air on-time record86.8%
- Frontier Airlines on-time record85.2%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. MIA to IAH and IAH to MIA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.