Carrier route record
DLATL→IAH
Delta Air Lines · Atlanta to Houston
- Flights
- 2,508
- Period
- July 2025 to June 2026
- Share of route
- 51%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on ATL to IAH sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land about 55 minutes behind schedule. That rests on 2,508 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,255 at 85.1% on time.
United Airlines is the most reliable of the three carriers covered here at 85.1% on time across 1,255 flights.
Key figures
On time
75.9%
Arrivals under 15 minutes late, of 2,455 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
1.95%
National rate is 1.81%
Whole route
76.4%
Every carrier on ATL to IAH, 4,914 flights
These figures cover 2,508 flights between July 2025 and June 2026. The median arrival is 3 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
Delta against every carrier on ATL to IAH
Delta flew 2,508 of the 4,914 flights on ATL to IAH, most of the route. Its 75.9% on time is about level with the route as a whole at 76.4%. Ranked by on-time rate it is number two 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. United Airlines arrives on time 85.1% 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 | 1,255 | 85.1% | 78 min | 1.12% | A |
| Delta Air Lines (this page) | 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.
Flight by flight
Delta flight numbers on ATL to IAH
Departure window
When Delta runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against 19 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am280 flights79.5%
- 8am–11am372 flights84.4%
- 11am–2pm424 flights83.3%
- 2pm–5pm567 flights69.0%
- 5pm–8pm231 flights65.7%
- 8pm–5am634 flights74.2%
Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 84.4% of the time, against 65.7% for the evening window. That is 19 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 634 flights scheduled in it.
Across the year
Delta on ATL to IAH through the year
July is the worst month at 64.9% on time, 23 points below September, the best at 88.0%. 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. May was the busiest month here, with 240 flights.
Across the week, Wednesday is the strongest day at 80.5% on time and Sunday the weakest at 71.2%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Delta runs late on this route
One category carries most of the weight here. Carrier accounts for 46% of the 32,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 46%Carrier
- 29%National Airspace System
- 20%Late-arriving aircraft
- 5%Extreme weather
The largest share of delay minutes, 46%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 15,000 of the 32,000 delay minutes reported here. The split is drawn from 32,463 reported delay minutes.
Cancellations sit at 1.95% against a national 1.81%, which is ordinary. Diversions add another 0.16%.
Connections and stage length
What a delay here costs
7.5% 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 55 minutes, 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 80.2% on time across 2,507 flights, 4 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 4 points of difference.
The sample behind these figures is 2,508 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 Delta on ATL to IAH
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 88.0% on time and July 64.9%, a swing of 23 points. If the dates move at all, move them out of July before you think about anything else. 2,455 completed flights over 12 months sit behind that.
Related
Where to go next
- ATL to IAH, every carrier
- Delta on IAH to ATL, the return leg
- United Airlines on ATL to IAH85.1%
- Frontier Airlines on ATL to IAH68.9%
- Spirit Airlines on ATL to IAH66.3%
- Delta Air Lines network-wide record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- Same route, different airline: where the carrier you pick matters most
- 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.