Houston, TX · departure reliability
IAH
George Bush Intercontinental
- Departures
- 118,936
- Period
- September 2025 to August 2026
- Carriers
- 11
- US rank
- #17 by volume
Houston
George Bush Intercontinental lands a B, 2 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 118,936 flights, of which Delta Air Lines flew 8,429 at 81.0% on time.
Delta Air Lines is the most reliable of the eleven carriers covered here at 81.0% on time across 8,429 flights.
Key figures
On time
79.1%
Departures arriving under 15 minutes late at their destination
Avg delay
75 min
Across delayed flights only
Cancelled
1.10%
National rate is 1.89%
Best carrier
Delta
81.0% on time here
These figures cover 119,000 flights between September 2025 and August 2026. The median arrival is 7 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
Which airlines run best out of IAH
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.0% of the time; JetBlue Airways manages 50.5%. Sample sizes sit next to every figure, because a two-point gap across 835 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 74,201 | 80.6% | 63 min | 0.55% | B+ |
| SkyWest Airlines | 14,187 | 77.8% | 94 min | 1.02% | B |
| Delta Air Lines | 8,429 | 81.0% | 83 min | 1.90% | B |
| American Airlines | 7,927 | 77.5% | 122 min | 2.35% | B |
| Frontier Airlines | 5,339 | 70.9% | 86 min | 2.38% | C |
| Spirit Airlines | 4,114 | 74.5% | 73 min | 3.23% | C− |
| Envoy Air | 1,270 | 78.0% | 91 min | 1.81% | B |
| Alaska Airlines | 1,195 | 80.6% | 55 min | 0.67% | B+ |
| Republic Airways | 873 | 74.8% | 79 min | 4.12% | C− |
| JetBlue Airways | 835 | 50.5% | 103 min | 4.79% | F− |
| PSA Airlines | 566 | 68.1% | 123 min | 6.89% | C− |
PSA Airlines cancels 6.9% 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
Busiest routes out of IAH
Route-level records vary far more than the airport average. These are the 25 busiest departures from IAH, each with its own on-time rate against the airport-wide 79.1%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| IAH to ORD · Chicago | 6,142 | 75.1% | 83 min | 1.50% | B |
| IAH to DFW · Dallas-Fort Worth | 5,800 | 76.4% | 98 min | 2.34% | B |
| IAH to LAX · Los Angeles | 5,147 | 84.1% | 62 min | 0.45% | B+ |
| IAH to ATL · Atlanta | 4,960 | 76.8% | 68 min | 1.92% | B |
| IAH to DEN · Denver | 4,728 | 83.0% | 69 min | 0.40% | B+ |
| IAH to LGA · New York | 3,991 | 72.8% | 82 min | 2.93% | C |
| IAH to EWR · Newark | 3,717 | 75.4% | 71 min | 1.86% | B |
| IAH to MIA · Miami | 3,665 | 78.6% | 93 min | 1.28% | B |
| IAH to SFO · San Francisco | 3,578 | 78.2% | 62 min | 0.42% | B+ |
| IAH to MCO · Orlando | 3,569 | 83.2% | 80 min | 1.04% | B |
| IAH to LAS · Las Vegas | 3,409 | 82.8% | 71 min | 0.85% | B+ |
| IAH to DCA · Washington | 3,337 | 75.3% | 75 min | 2.31% | B |
| IAH to PHX · Phoenix | 2,980 | 79.9% | 87 min | 0.74% | B+ |
| IAH to FLL · Fort Lauderdale | 2,923 | 78.5% | 67 min | 1.27% | B |
| IAH to MSY · New Orleans | 2,911 | 83.8% | 64 min | 0.14% | B+ |
| IAH to AUS · Austin | 2,671 | 80.2% | 62 min | 0.71% | B+ |
| IAH to SAT · San Antonio | 2,373 | 83.1% | 58 min | 0.38% | B+ |
| IAH to CLT · Charlotte | 2,314 | 81.8% | 108 min | 1.82% | B |
| IAH to DTW · Detroit | 2,088 | 78.9% | 74 min | 1.10% | B |
| IAH to SEA · Seattle | 2,072 | 80.7% | 52 min | 0.24% | B+ |
| IAH to BOS · Boston | 2,017 | 71.5% | 78 min | 1.49% | C |
| IAH to MSP · Minneapolis | 1,939 | 79.2% | 85 min | 0.93% | B+ |
| IAH to SLC · Salt Lake City | 1,932 | 83.4% | 78 min | 0.47% | B+ |
| IAH to PHL · Philadelphia | 1,878 | 78.8% | 90 min | 1.86% | B |
| IAH to IAD · Washington | 1,860 | 82.4% | 62 min | 0.43% | B+ |
Departure window
The best time of day to leave IAH
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 31 points between the best and worst carrier.
- 5am–8am19,396 flights89.2%
- 8am–11am17,297 flights82.6%
- 11am–2pm19,654 flights79.9%
- 2pm–5pm21,348 flights76.9%
- 5pm–8pm21,365 flights71.5%
- 8pm–5am19,876 flights76.2%
Scale runs 65% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.2% of the time, against 71.5% 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 5pm–8pm window is the busiest, with 21,365 flights scheduled in it.
Explore
Filter IAH departures 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 departures from Houston (IAH), the best departure window is 5am–8am at 89.2% on time and the worst is 5pm–8pm at 71.5%, a wide gap of 17.7 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am89.2%
- 8–11am82.6%
- 11am–2pm79.9%
- 2–5pm76.9%
- 5–8pm71.5%
- 8pm–5am76.2%
best all US flightsScale 60% to 95%.
Across the year
When IAH runs late
IAH's year swings by 16 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.
June is the worst month at 69.9% on time, 16 points below January, the best at 85.7%. 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. March was the busiest month here, with 10,492 flights.
Across the week, Tuesday is the strongest day at 82.8% on time and Sunday the weakest at 75.1%, a spread of 8 points.
IAH month by month
From Europe
Transatlantic routes into IAH
5 European airports send scheduled passenger flights to IAH, 6,744 flights a year in both directions by the DOT's international count. The DOT keeps no delay record for international flights; the UK routes carry the CAA's departure punctuality, and every route sets its departure airport's EUROCONTROL figures beside IAH's own record above.
Delay causes
Why IAH 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 1.84 million reported delay minutes.
- 37%Late-arriving aircraft
- 33%Carrier
- 24%National Airspace System
- 6%Extreme weather
- 0%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 1.84 million reported delay minutes here, that single category outweighs weather by 7 to one. The split is drawn from 1,843,734 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 89.2% on time here.
Cancellations sit at 1.10% against a national 1.89%, which is ordinary. Diversions add another 0.28%.
7.8% 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.
118,936 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
What to do with this
Flying out of IAH
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 85.7% on time and June 69.9%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 117,298 completed flights over 12 months sit behind that.
Common questions
IAH delay questions
How often is Houston (IAH) delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 20.9% of the 118,936 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 Houston (IAH)?
Delta Air Lines leads at 81.0% on time across 8,429 flights. JetBlue Airways is at the other end on 50.5%, a gap of 31 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 Houston (IAH)?
The 5am–8am departure window is the strongest at 89.2% on time. The 5pm–8pm window is the weakest at 71.5%, 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 June delays on Houston (IAH)?
June is the weakest month at 69.9% on time, compared with 85.7% in January. Across the year that is 16 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 ORD — Chicago75.1%
- IAH to DFW — Dallas-Fort Worth76.4%
- IAH to LAX — Los Angeles84.1%
- IAH to ATL — Atlanta76.8%
- IAH to DEN — Denver83.0%
- IAH to LGA — New York72.8%
- United Airlines on-time record80.6%
- SkyWest Airlines on-time record77.8%
- Delta Air Lines on-time record81.0%
- American Airlines on-time record77.5%
- Why the first flight of the morning is statistically safest
- Dallas and Houston airports, plus Austin and San Antonio
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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.