Route reliability record
ORD→IAH
Chicago to Houston
- Flights
- 6,141
- Period
- September 2025 to August 2026
- Distance
- 925 mi
- Carriers
- 7
This route lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 6,141 ORD to IAH flights, of which United Airlines flew 4,080 at 80.0% on time.
Best time to fly ORD to IAH: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 88.2% of the time and Tuesday flights 81.0%, against 76.0% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.0%
Arrivals under 15 minutes late, of 6,041 completed flights
Avg delay
74 min
Across delayed arrivals only, not all flights
Cancelled
1.40%
National rate is 1.89%
Best carrier
United
80.0% on time across 4,080 flights
These figures cover 6,141 flights between September 2025 and August 2026. Beyond the headline rate, 9.6% 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 ORD to IAH
The choice of carrier is not cosmetic here. United Airlines arrives on time 80.0% of the time; American Airlines manages 59.8%. Sample sizes sit next to every figure, because a two-point gap across 882 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 4,080 | 80.0% | 70 min | 0.66% | B+ |
| Frontier Airlinesthin sample | 276 | 78.6% | 103 min | 3.26% | B− |
| Republic Airwaysthin sample | 311 | 76.6% | 73 min | 2.25% | B |
| Envoy Airthin sample | 349 | 74.6% | 63 min | 1.43% | C |
| Spirit Airlinesthin sample | 241 | 65.7% | 90 min | 4.56% | C− |
| American Airlines | 882 | 59.8% | 81 min | 3.06% | D− |
| SkyWest Airlinesthin sample | 2 | 0.0% | 32 min | 0.00% | F+ |
American Airlines cancels 3.1% 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
Flights on ORD to IAH
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 Chicago to Houston
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. 1 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ORD → IAHChicago to Houston | United Airlines | 79.5% | 80.0% | 0.66% | 5am–8am, Tue | UA 1231 07:35 |
| 2. MDW → HOUChicago to Houston | Southwest Airlines | 72.4% | 73.3% | 1.24% | 5am–8am, Wed | — |
| 3. ORD → IAHChicago to Houston | American Airlines | 58.0% | 59.8% | 3.06% | 8am–11am, Tue | AA 3144 20:59 |
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 24 points, against 20 points between the best and worst carrier.
- 5am–8am1,092 flights88.2%
- 8am–11am1,222 flights81.6%
- 11am–2pm676 flights82.5%
- 2pm–5pm1,258 flights69.1%
- 5pm–8pm860 flights71.2%
- 8pm–5am1,033 flights64.4%
Scale runs 55% to 95%.
The 8pm–5am window is where this operation falls apart: 64.4% on time, against 88.2% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 2pm–5pm window is the busiest, with 1,258 flights scheduled in it.
Explore
Filter ORD to IAH 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 ORD to IAH, the best departure window is 5am–8am at 88.2% on time and the worst is 8pm–5am at 64.4%, a wide gap of 23.8 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am88.2%
- 8–11am81.6%
- 11am–2pm82.5%
- 2–5pm69.1%
- 5–8pm71.2%
- 8pm–5am64.4%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route'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 69.7% on time, 16 points below February, the best at 86.1%. 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. August was the busiest month here, with 558 flights.
Across the week, Tuesday is the strongest day at 81.0% on time and Sunday the weakest at 71.4%, a spread of 10 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 45% of the 108,000 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Late-arriving aircraft
- 24%National Airspace System
- 24%Carrier
- 7%Extreme weather
- 0%Security
45% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 108,000 reported delay minutes here, that single category outweighs weather by 7 to one. The split is drawn from 107,681 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 88.2% on time here.
Cancellations sit at 1.40% against a national 1.89%, which is ordinary. Diversions add another 0.23%.
Connections and stage length
What a delay here actually costs
9.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The 925 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 75.1% on time across 6,142 flights, within about 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 6,141 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 IAH 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. February runs 86.1% on time and June 69.7%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 6,041 completed flights over 12 months sit behind that.
Common questions
ORD to IAH questions
How often is ORD to IAH 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 24.0% of the 6,141 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 ORD to IAH?
United Airlines leads at 80.0% on time across 4,080 flights. American Airlines is at the other end on 59.8%, 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 ORD to IAH?
The 5am–8am departure window is the strongest at 88.2% on time. The 8pm–5am window is the weakest at 64.4%, 24 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 ORD to IAH?
June is the weakest month at 69.7% on time, compared with 86.1% in February. 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 — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on ORD to IAH80.0%
- Frontier Airlines on ORD to IAH78.6%
- Republic Airways on ORD to IAH76.6%
- Envoy Air on ORD to IAH74.6%
- Spirit Airlines on ORD to IAH65.7%
- American Airlines on ORD to IAH59.8%
- ORD to LGA, a related route66.6%
- DFW to IAH, a related route70.7%
- ORD to BOS, a related route66.6%
- United Airlines on-time record80.0%
- Frontier Airlines on-time record78.6%
- Republic Airways on-time record76.6%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. ORD to IAH and IAH to ORD 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.