Route reliability record
IAH→ATL
Houston to Atlanta
- Flights
- 4,960
- Period
- September 2025 to August 2026
- Distance
- 689 mi
- Carriers
- 5
This route lands a B, level with the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 4,960 IAH to ATL flights, of which Delta Air Lines flew 2,543 at 80.4% on time.
Best time to fly IAH to ATL: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 84.2% of the time and Wednesday flights 82.1%, against 76.8% for the route overall.
Delta Air Lines is the most reliable of the three carriers covered here at 80.4% on time across 2,543 flights.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 4,859 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
1.92%
National rate is 1.89%
Best carrier
Delta
80.4% on time across 2,543 flights
These figures cover 4,960 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 IAH to ATL
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 80.4% of the time; Frontier Airlines manages 61.7%. 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 |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 6 | 83.3% | 20 min | 0.00% | B+ |
| Delta Air Lines | 2,543 | 80.4% | 70 min | 2.04% | B |
| United Airlines | 1,283 | 79.8% | 64 min | 0.47% | B+ |
| Spirit Airlinesthin sample | 301 | 74.7% | 58 min | 5.32% | C− |
| Frontier Airlines | 827 | 61.7% | 70 min | 2.54% | D |
The spread between Delta and Frontier is 19 points, wide enough that it should decide the booking. On a hundred trips that is 19 more arrivals inside the on-time window.
Flight by flight
Flights on IAH to ATL
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 Houston to Atlanta
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. HOU → ATLHouston to Atlanta | Delta Air Lines | 82.8% | 84.6% | 2.09% | 5am–8am, Thu | DL 2557 06:00 |
| 2. IAH → ATLHouston to Atlanta | United Airlines | 79.4% | 79.8% | 0.47% | 5am–8am, Tue | UA 1030 07:20 |
| 3. IAH → ATLHouston to Atlanta | Delta Air Lines | 78.8% | 80.4% | 2.04% | 5am–8am, Wed | DL 1069 05:30 |
| 4. HOU → ATLHouston to Atlanta | Southwest Airlines | 73.7% | 74.2% | 0.61% | 5am–8am, Fri | — |
| 5. IAH → ATLHouston to Atlanta | Frontier Airlines | 60.1% | 61.7% | 2.54% | 8am–11am, Thu | F9 1404 06:00 |
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 19 points between the best and worst carrier.
- 5am–8am1,484 flights84.2%
- 8am–11am542 flights81.1%
- 11am–2pm857 flights79.5%
- 2pm–5pm798 flights73.9%
- 5pm–8pm943 flights66.0%
- 8pm–5am336 flights68.4%
Scale runs 60% to 90%.
Book the early departure. Flights leaving between 5am–8am arrive on time 84.2% of the time, against 66.0% for the evening window. That is 18 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 1,484 flights scheduled in it.
Explore
Filter IAH to ATL 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 IAH to ATL, the best departure window is 5am–8am at 84.2% on time and the worst is 5pm–8pm at 66.0%, a wide gap of 18.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am84.2%
- 8–11am81.1%
- 11am–2pm79.5%
- 2–5pm73.9%
- 5–8pm66.0%
- 8pm–5am68.4%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 25 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.
September is the best month on the calendar at 91.1% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. April was the busiest month here, with 466 flights.
Across the week, Wednesday is the strongest day at 82.1% on time and Sunday the weakest at 68.3%, 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 76,000 reported delay minutes.
- 39%Late-arriving aircraft
- 33%Carrier
- 25%National Airspace System
- 2%Extreme weather
- 0%Security
39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 76,000 reported delay minutes here, that single category outweighs weather by 18 to one. The split is drawn from 76,350 reported delay minutes.
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 84.2% on time here.
Cancellations sit at 1.92% against a national 1.89%, which is ordinary. Diversions add another 0.12%.
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 about 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 76.9% on time across 4,965 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 4,960 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 ATL 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 91.1% on time and March 65.9%, a swing of 25 points. If the dates move at all, move them out of March before you think about anything else. 4,859 completed flights over 12 months sit behind that.
Common questions
IAH to ATL questions
How often is IAH to ATL delayed?
About 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 23.2% of the 4,960 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on IAH to ATL?
Delta Air Lines leads at 80.4% on time across 2,543 flights. Frontier Airlines is at the other end on 61.7%, a gap of 19 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 IAH to ATL?
The 5am–8am departure window is the strongest at 84.2% on time. The 5pm–8pm window is the weakest at 66.0%, 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 March delays on IAH to ATL?
March is the weakest month at 65.9% on time, compared with 91.1% in September. Across the year that is 25 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
- ATL to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on IAH to ATL80.4%
- United Airlines on IAH to ATL79.8%
- Spirit Airlines on IAH to ATL74.7%
- Frontier Airlines on IAH to ATL61.7%
- IAH to ORD, a related route75.1%
- LGA to ATL, a related route75.5%
- IAH to DFW, a related route76.4%
- SkyWest Airlines on-time record83.3%
- Delta Air Lines on-time record80.4%
- United Airlines on-time record79.8%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. IAH to ATL and ATL to IAH 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.