Carrier performance at one airport
DL→IAH
Delta Air Lines at George Bush Intercontinental
- Departures
- 8,369
- Period
- July 2025 to June 2026
- Routes
- 7
- Rank here
- #1 of 11
Delta Air Lines at Houston lands a B, 3 points better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 8,369 flights, of which Delta Air Lines flew 8,369 at 80.8% on time.
Measured against the airport rather than the country, Delta Air Lines runs 2 points ahead of the 78.4% weighted average across all carriers at IAH. That is the comparison worth making: every operator here works the same runways, the same airspace and the same weather.
Key figures
On time
80.8%
8,194 completed departures
Avg delay
83 min
Across delayed flights only
Cancelled
1.78%
At IAH, this carrier only
Rank here
#1
Of 11 carriers clearing the floor at IAH
These figures cover 8,369 flights between July 2025 and June 2026. The median arrival is 8 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.
Against the competition
Every carrier at IAH, ranked
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 80.8% of the time; JetBlue Airways manages 61.1%. Sample sizes sit next to every figure, because a two-point gap across 542 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines (this page) | 8,369 | 80.8% | 83 min | 1.78% | B |
| United Airlines | 74,010 | 79.6% | 65 min | 0.67% | B+ |
| Alaska Airlines | 1,205 | 78.5% | 54 min | 0.83% | B+ |
| Envoy Air | 1,388 | 77.0% | 85 min | 2.23% | B |
| SkyWest Airlines | 14,351 | 76.8% | 92 min | 1.16% | B |
| American Airlines | 7,752 | 76.7% | 128 min | 2.62% | B |
| Spirit Airlines | 5,410 | 74.7% | 74 min | 2.81% | C |
| Republic Airways | 905 | 73.7% | 76 min | 4.20% | C− |
| Frontier Airlines | 4,776 | 70.1% | 86 min | 1.74% | C |
| PSA Airlines | 379 | 69.0% | 131 min | 4.22% | C− |
| JetBlue Airways | 542 | 61.1% | 84 min | 1.85% | D |
PSA Airlines cancels 4.2% 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.
Route by route
Where Delta Air Lines flies from IAH
Delta Air Lines operates 7 routes out of IAH with enough volume to report. Route records inside one carrier at one airport still spread widely, because a short shuttle and a transcontinental have very different exposure to a late inbound.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| IAH to ATL · Atlanta | 2,507 | 80.2% | 66 min | 2.07% | B |
| IAH to LGA · New York | 1,342 | 77.2% | 95 min | 3.95% | B− |
| IAH to DTW · Detroit | 1,322 | 82.3% | 76 min | 0.76% | B+ |
| IAH to MSP · Minneapolis | 1,272 | 78.9% | 98 min | 1.02% | B |
| IAH to SLC · Salt Lake City | 1,011 | 82.7% | 93 min | 0.30% | B+ |
| IAH to LAX · Los Angeles | 645 | 88.5% | 86 min | 1.09% | A |
| IAH to JFK · New Yorkthin sample | 269 | 78.9% | 86 min | 4.09% | B− |
Departure window
Best time of day for this operation
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 21 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am2,526 flights89.2%
- 8am–11am817 flights81.6%
- 11am–2pm1,635 flights80.4%
- 2pm–5pm1,745 flights76.7%
- 5pm–8pm1,586 flights72.2%
- 8pm–5am60 flights67.8%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.2% of the time, against 67.8% for the overnight window. That is 21 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 2,526 flights scheduled in it.
Across the year
Seasonal pattern
December is the weak month at 73.4% on time, against 91.9% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 767 flights.
Delay causes
What holds this operation up
- 44%Carrier
- 36%Late-arriving aircraft
- 17%National Airspace System
- 3%Extreme weather
- 0%Security
36% 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 130,000 reported delay minutes here, that single category outweighs weather by 11 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 130,275 reported delay minutes.
Cancellations sit at 1.78% against a national 1.81%, which is ordinary. Diversions add another 0.31%.
7.3% 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 are the an hour and a half kind, which a normal layover absorbs.
The sample behind these figures is 8,369 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.
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 91.9% on time and December 73.4%, a swing of 19 points. If the dates move at all, move them out of December before you think about anything else. 8,194 completed flights over 12 months sit behind that.
Common questions
Delta Air Lines at IAH
How often is Delta Air Lines at IAH delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.2% of the 8,369 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on Delta Air Lines at IAH?
Delta Air Lines leads at 80.8% on time across 8,369 flights. JetBlue Airways is at the other end on 61.1%, a gap of 20 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 Delta Air Lines at IAH?
The 5am–8am departure window is the strongest at 89.2% on time. The 8pm–5am window is the weakest at 67.8%, 21 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 December delays on Delta Air Lines at IAH?
December is the weakest month at 73.4% on time, compared with 91.9% in September. Across the year that is 19 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
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.