Route reliability record
ATL→IAH
Atlanta to Houston
- Flights
- 4,965
- Period
- September 2025 to August 2026
- Distance
- 689 mi
- Carriers
- 5
This route lands a B, level with the national rate of 77.3%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 4,965 ATL to IAH flights, of which United Airlines flew 1,281 at 85.3% on time.
Best time to fly ATL to IAH: a 11am–2pm departure, ideally on a Wednesday. Flights in that window arrived on time 86.7% of the time and Wednesday flights 81.8%, against 76.9% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 85.3% on time across 1,281 flights.
Key figures
On time
76.9%
Arrivals under 15 minutes late, of 4,869 completed flights
Avg delay
69 min
Across delayed arrivals only, not all flights
Cancelled
1.79%
National rate is 1.89%
Best carrier
United
85.3% on time across 1,281 flights
These figures cover 4,965 flights between September 2025 and August 2026. Beyond the headline rate, 8.5% 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 ATL to IAH
The choice of carrier is not cosmetic here. United Airlines arrives on time 85.3% of the time; Frontier Airlines manages 69.5%. Sample sizes sit next to every figure, because a two-point gap across 827 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,281 | 85.3% | 74 min | 0.70% | A+ |
| SkyWest Airlinesthin sample | 6 | 83.3% | 46 min | 0.00% | B+ |
| Delta Air Lines | 2,543 | 76.0% | 57 min | 1.97% | B |
| Frontier Airlines | 827 | 69.5% | 87 min | 1.57% | C |
| Spirit Airlinesthin sample | 308 | 67.9% | 81 min | 5.52% | C− |
The spread between United and Frontier 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 ATL 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 Atlanta 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. 2 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ATL → IAHAtlanta to Houston | United Airlines | 84.7% | 85.3% | 0.70% | 8am–11am, Wed | — |
| 2. ATL → HOUAtlanta to Houston | Delta Air Lines | 78.9% | 80.6% | 2.09% | 8am–11am, Wed | DL 1509 08:10 |
| 3. ATL → HOUAtlanta to Houston | Southwest Airlines | 78.8% | 79.5% | 0.82% | 5am–8am, Wed | — |
| 4. ATL → IAHAtlanta to Houston | Delta Air Lines | 74.5% | 76.0% | 1.97% | 8am–11am, Wed | DL 1682 10:10 |
| 5. ATL → IAHAtlanta to Houston | Frontier Airlines | 68.4% | 69.5% | 1.57% | 5pm–8pm, Thu | F9 1403 06:07 |
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 18 points, against 16 points between the best and worst carrier.
- 5am–8am852 flights83.5%
- 8am–11am696 flights82.7%
- 11am–2pm701 flights86.7%
- 2pm–5pm1,091 flights72.7%
- 5pm–8pm556 flights70.5%
- 8pm–5am1,069 flights69.0%
Scale runs 60% to 90%.
The best window here is not the first bank but the 11am–2pm slot at 86.7% on time, ahead of 8pm–5am at 69.0%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 2pm–5pm window is the busiest, with 1,091 flights scheduled in it.
Explore
Filter ATL 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 ATL to IAH, the best departure window is 11am–2pm at 86.7% on time and the worst is 8pm–5am at 69.0%, a wide gap of 17.7 points. All US flights leaving 11am–2pm ran 78.3%.
- 5–8am83.5%
- 8–11am82.7%
- 11am–2pm86.7%
- 2–5pm72.7%
- 5–8pm70.5%
- 8pm–5am69.0%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 21 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.
July is the worst month at 65.6% on time, 21 points below September, the best at 86.2%. 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 469 flights.
Across the week, Wednesday is the strongest day at 81.8% on time and Sunday the weakest at 71.3%, a spread of 11 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 77,000 reported delay minutes.
- 39%Carrier
- 36%Late-arriving aircraft
- 22%National Airspace System
- 3%Extreme weather
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 77,000 reported delay minutes here, that single category outweighs weather by 12 to one. The split is drawn from 77,140 reported delay minutes.
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 30,000 of the 77,000 delay minutes reported here.
Cancellations sit at 1.79% against a national 1.89%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
8.5% 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 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.
The return leg runs 76.8% on time across 4,960 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 4,965 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. September runs 86.2% on time and July 65.6%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else. 4,869 completed flights over 12 months sit behind that.
Common questions
ATL to IAH questions
How often is ATL to IAH delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.1% of the 4,965 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 ATL to IAH?
United Airlines leads at 85.3% on time across 1,281 flights. Frontier Airlines is at the other end on 69.5%, 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 ATL to IAH?
The 11am–2pm departure window is the strongest at 86.7% on time. The 8pm–5am window is the weakest at 69.0%, 18 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 July delays on ATL to IAH?
July is the weakest month at 65.6% on time, compared with 86.2% in September. Across the year that is 21 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 ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on ATL to IAH85.3%
- Delta Air Lines on ATL to IAH76.0%
- Frontier Airlines on ATL to IAH69.5%
- Spirit Airlines on ATL to IAH67.9%
- ATL to LGA, a related route72.3%
- ORD to IAH, a related route76.0%
- ATL to MCO, a related route70.3%
- United Airlines on-time record85.3%
- SkyWest Airlines on-time record83.3%
- Delta Air Lines on-time record76.0%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. ATL to IAH and IAH to ATL 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.