Airport month record
IAHAUG
George Bush Intercontinental in August 2025
- Departures
- 9,889
- Month
- August 2025
- National, same month
- 77.4%
- Carriers
- 10
Historical statistics for August 2025, not live status or a forecast for this year’s August. For today’s conditions at IAH, see live FAA status.
IAH in August sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.4%. The late ones land a little over an hour behind schedule. That rests on 9,889 flights, of which Delta Air Lines flew 695 at 81.9% on time.
Delta Air Lines is the most reliable of the five carriers covered here at 81.9% on time across 695 flights.
Key figures
On time
74.1%
Arrivals under 15 minutes late, of 9,772 completed departures
Avg delay
74 min
Across delayed arrivals only, not all flights
Cancelled
0.87%
Nationally in August: 1.08%
Whole year
78.4%
IAH across all twelve months
These figures cover 9,889 departures from George Bush Intercontinental in August 2025. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.
Against the year
August next to IAH's other months
Against IAH's own year, August ran 4 points worse than the twelve-month rate of 78.4%, which makes it number ten of twelve months, best first. Either side of it, July ran 68.8% on time and September 85.6%, so a trip moved by a few weeks would have landed in a better stretch.
| Month | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| July 2025 | 10,311 | 68.8% | 88 min | 1.74% | C |
| August 2025 (this page) | 9,889 | 74.1% | 74 min | 0.87% | C+ |
| September 2025 | 9,493 | 85.6% | 69 min | 0.20% | A+ |
| October 2025 | 10,247 | 80.7% | 65 min | 0.30% | B+ |
| November 2025 | 10,022 | 78.2% | 73 min | 1.06% | B |
| December 2025 | 9,971 | 79.4% | 71 min | 0.60% | B+ |
| January 2026 | 9,656 | 85.7% | 74 min | 3.07% | A− |
| February 2026 | 8,976 | 85.6% | 68 min | 1.06% | A |
| March 2026 | 10,492 | 76.4% | 95 min | 2.89% | B |
| April 2026 | 10,022 | 80.4% | 69 min | 0.57% | B+ |
| May 2026 | 10,105 | 77.1% | 73 min | 0.46% | B+ |
| June 2026 | 9,903 | 69.9% | 79 min | 0.75% | C+ |
Departure window
The best time of day to leave IAH in August
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,651 flights89.0%
- 8am–11am1,399 flights80.6%
- 11am–2pm1,510 flights71.5%
- 2pm–5pm1,701 flights70.3%
- 5pm–8pm1,873 flights65.0%
- 8pm–5am1,755 flights70.7%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.0% of the time, against 65.0% for the evening window. That is 24 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 1,873 flights scheduled in it.
Across the week, Tuesday is the strongest day at 79.8% on time and Friday the weakest at 66.4%. 13 points is a smaller lever than departure hour, but it is free.
Carrier by carrier
Which airlines ran best at IAH in August
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.9% of the time; American Airlines manages 68.1%. Sample sizes sit next to every figure, because a two-point gap across 696 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 5,971 | 74.1% | 66 min | 0.74% | C+ |
| SkyWest Airlines | 1,260 | 74.9% | 69 min | 0.08% | C+ |
| American Airlines | 696 | 68.1% | 139 min | 2.87% | C |
| Delta Air Lines | 695 | 81.9% | 74 min | 0.58% | B+ |
| Spirit Airlines | 630 | 77.2% | 66 min | 0.63% | B+ |
| Frontier Airlinesthin sample | 320 | 67.6% | 96 min | 2.19% | C |
| Alaska Airlinesthin sample | 121 | 73.1% | 38 min | 1.65% | C |
| Envoy Airthin sample | 79 | 67.5% | 83 min | 1.27% | C |
| Republic Airwaysthin sample | 59 | 67.9% | 61 min | 3.39% | C− |
| JetBlue Airwaysthin sample | 54 | 60.4% | 78 min | 1.85% | D |
The spread between Delta and American is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.
Route by route
Busiest routes out of IAH in August
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| IAH to ORD · Chicago | 535 | 73.4% | 87 min | 2.06% | C |
| IAH to DFW · Dallas-Fort Worth | 465 | 64.0% | 104 min | 2.58% | D |
| IAH to LAX · Los Angeles | 442 | 86.2% | 52 min | 0.90% | A+ |
| IAH to DEN · Denver | 403 | 73.2% | 70 min | 0.25% | C+ |
| IAH to ATL · Atlanta | 379 | 79.7% | 71 min | 1.32% | B |
| IAH to LGA · New York | 376 | 72.6% | 71 min | 0.80% | C+ |
| IAH to EWR · Newarkthin sample | 338 | 69.5% | 75 min | 0.30% | C+ |
| IAH to MCO · Orlandothin sample | 300 | 65.6% | 84 min | 0.67% | C+ |
| IAH to MIA · Miamithin sample | 300 | 72.1% | 89 min | 0.67% | C+ |
| IAH to SFO · San Franciscothin sample | 299 | 80.5% | 72 min | 0.67% | B+ |
| IAH to LAS · Las Vegasthin sample | 286 | 79.2% | 72 min | 1.05% | B |
| IAH to MSY · New Orleansthin sample | 248 | 80.6% | 61 min | 0.40% | B+ |
| IAH to SEA · Seattlethin sample | 228 | 68.9% | 50 min | 1.32% | C |
| IAH to AUS · Austinthin sample | 214 | 76.5% | 67 min | 0.47% | B+ |
| IAH to SAT · San Antoniothin sample | 208 | 78.7% | 59 min | 0.48% | B+ |
| IAH to DCA · Washingtonthin sample | 207 | 62.6% | 60 min | 0.48% | D+ |
| IAH to DTW · Detroitthin sample | 206 | 77.8% | 55 min | 0.97% | B+ |
| IAH to PHX · Phoenixthin sample | 197 | 72.8% | 76 min | 1.02% | C |
| IAH to BOS · Bostonthin sample | 196 | 71.8% | 75 min | 0.51% | C+ |
| IAH to FLL · Fort Lauderdalethin sample | 194 | 78.1% | 52 min | 1.03% | B |
| IAH to CLT · Charlottethin sample | 182 | 70.8% | 73 min | 1.65% | C |
| IAH to IAD · Washingtonthin sample | 174 | 73.6% | 64 min | 0.00% | C+ |
| IAH to SLC · Salt Lake Citythin sample | 160 | 77.4% | 59 min | 0.62% | B+ |
| IAH to TPA · Tampathin sample | 147 | 77.2% | 55 min | 0.68% | B+ |
| IAH to PHL · Philadelphiathin sample | 143 | 73.9% | 252 min | 3.50% | C− |
Delay causes
What held IAH up in August
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 187,000 reported delay minutes.
- 38%Late-arriving aircraft
- 34%Carrier
- 21%National Airspace System
- 7%Extreme weather
38% 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 187,000 reported delay minutes here, that single category outweighs weather by 6 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 186,744 reported delay minutes.
Cancellations are rare at 0.87%, below the national 1.08% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.0% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
What to do with this
Flying from IAH in August
For a August trip through IAH: plan on this being one of the airport's harder months. The 5am–8am departures held up best at 89.0% on time, and with 10.0% of arrivals an hour or more late, a connection here deserves more slack than the same trip in January would.
Related
Where to go next
- George Bush Intercontinental (IAH), the whole year
- IAH in July68.8%
- IAH in September85.6%
- IAH in October80.7%
- IAH in November78.2%
- IAH in December79.4%
- IAH in January85.7%
- IAH in February85.6%
- IAH in March76.4%
- IAH in April80.4%
- IAH in May77.1%
- IAH in June69.9%
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.