Carrier route record
UAATL→IAH
United Airlines · Atlanta to Houston
- Flights
- 1,255
- Period
- July 2025 to June 2026
- Share of route
- 26%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on ATL to IAH earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 1,255 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,508 at 75.9% on time.
Set against the rest of the country, United's ATL to IAH record is 8 points better than the US average of 77.6%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.
Key figures
On time
85.1%
Arrivals under 15 minutes late, of 1,240 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
1.12%
National rate is 1.81%
Whole route
76.4%
Every carrier on ATL to IAH, 4,914 flights
These figures cover 1,255 flights between July 2025 and June 2026. The median arrival is 11 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 ATL to IAH
United flew 1,255 of the 4,914 flights on ATL to IAH, about 26% of it. Its 85.1% on time is 9 points better than the route as a whole, which runs 76.4%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 85.1% to Spirit at 66.3%.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 75.9% of the time; Spirit Airlines manages 66.3%. Sample sizes sit next to every figure, because a two-point gap across 384 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 1,255 | 85.1% | 78 min | 1.12% | A |
| Delta Air Lines | 2,508 | 75.9% | 55 min | 1.95% | B |
| Frontier Airlines | 767 | 68.9% | 82 min | 1.43% | C |
| Spirit Airlines | 384 | 66.3% | 76 min | 4.69% | C− |
Spirit Airlines cancels 4.7% 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 13 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am322 flights87.1%
- 8am–11am146 flights90.1%
- 11am–2pm310 flights89.9%
- 2pm–5pm236 flights80.4%
- 5pm–8pm241 flights77.6%
- 8pm–5am—
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 90.1% of the time, against 77.6% for the evening window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 322 flights scheduled in it.
Across the year
United on ATL to IAH through the year
June is the worst month at 72.5% on time, 20 points below February, the best at 92.7%. 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. April was the busiest month here, with 140 flights.
Across the week, Tuesday is the strongest day at 88.1% on time and Monday the weakest at 83.0%. 5 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 14,000 reported delay minutes.
- 39%Late-arriving aircraft
- 30%Carrier
- 29%National Airspace System
- 2%Extreme weather
39% 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 14,000 reported delay minutes here, that single category outweighs weather by 16 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 14,493 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.1% on time here.
Cancellations sit at 1.12% against a national 1.81%, which is ordinary. Diversions add another 0.08%.
Connections and stage length
What a delay here costs
6.1% 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 a little over an hour, which a normal layover absorbs.
The 689 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 81.9% on time across 1,257 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 1,255 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 ATL to IAH
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 92.7% on time and June 72.5%, a swing of 20 points. If the dates move at all, move them out of June before you think about anything else. 1,240 completed flights over 12 months sit behind that.
Related
Where to go next
- ATL to IAH, every carrier
- United on IAH to ATL, the return leg
- Delta Air Lines on ATL to IAH75.9%
- Frontier Airlines on ATL to IAH68.9%
- Spirit Airlines on ATL to IAH66.3%
- United Airlines network-wide record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- George Bush Intercontinental (IAH) 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.