Route reliability record
IAH→ORD
Houston to Chicago
- Flights
- 6,142
- Period
- September 2025 to August 2026
- Distance
- 925 mi
- Carriers
- 7
This route 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 77.3%. The late ones land an hour and a half behind schedule. That rests on 6,142 IAH to ORD flights, of which United Airlines flew 4,084 at 78.2% on time.
Best time to fly IAH to ORD: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 87.9% of the time and Tuesday flights 78.9%, against 75.1% 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
75.1%
Arrivals under 15 minutes late, of 6,007 completed flights
Avg delay
83 min
Across delayed arrivals only, not all flights
Cancelled
1.50%
National rate is 1.89%
Best carrier
United
78.2% on time across 4,084 flights
These figures cover 6,142 flights between September 2025 and August 2026. Beyond the headline rate, 10.0% 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 IAH to ORD
The choice of carrier is not cosmetic here. United Airlines arrives on time 78.2% of the time; American Airlines manages 67.3%. Sample sizes sit next to every figure, because a two-point gap across 883 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 4,084 | 78.2% | 69 min | 0.59% | B+ |
| Republic Airwaysthin sample | 309 | 74.6% | 85 min | 3.56% | C− |
| Envoy Airthin sample | 350 | 73.5% | 63 min | 1.14% | C |
| Frontier Airlinesthin sample | 275 | 67.8% | 143 min | 3.64% | C− |
| American Airlines | 883 | 67.3% | 118 min | 3.51% | C− |
| Spirit Airlinesthin sample | 239 | 61.7% | 71 min | 5.02% | D− |
| SkyWest Airlinesthin sample | 2 | 50.0% | 38 min | 0.00% | F+ |
American Airlines cancels 3.5% 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 IAH to ORD
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 Houston to Chicago
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. IAH → ORDHouston to Chicago | United Airlines | 77.7% | 78.2% | 0.59% | 5am–8am, Tue | UA 1617 08:23 |
| 2. HOU → MDWHouston to Chicago | Southwest Airlines | 69.9% | 70.6% | 0.98% | 5am–8am, Thu | — |
| 3. IAH → ORDHouston to Chicago | American Airlines | 64.9% | 67.3% | 3.51% | 8am–11am, Tue | — |
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 31 points, against 11 points between the best and worst carrier.
- 5am–8am1,408 flights87.9%
- 8am–11am958 flights85.3%
- 11am–2pm1,067 flights71.7%
- 2pm–5pm513 flights70.5%
- 5pm–8pm1,295 flights57.3%
- 8pm–5am901 flights76.4%
Scale runs 50% to 95%.
The 5pm–8pm window is where this operation falls apart: 57.3% on time, against 87.9% 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 5am–8am window is the busiest, with 1,408 flights scheduled in it.
Explore
Filter IAH to ORD 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 IAH to ORD, the best departure window is 5am–8am at 87.9% on time and the worst is 5pm–8pm at 57.3%, a wide gap of 30.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am87.9%
- 8–11am85.3%
- 11am–2pm71.7%
- 2–5pm70.5%
- 5–8pm57.3%
- 8pm–5am76.4%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 18 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.
September is the best month on the calendar at 85.8% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. August was the busiest month here, with 558 flights.
Across the week, Tuesday is the strongest day at 78.9% on time and Sunday the weakest at 70.2%, a spread of 9 points.
Delay causes
Why this route 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 124,000 reported delay minutes.
- 38%Late-arriving aircraft
- 38%National Airspace System
- 21%Carrier
- 3%Extreme weather
- 0%Security
38% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 124,000 reported delay minutes here, that single category outweighs weather by 13 to one. The split is drawn from 123,616 reported delay minutes.
38% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 47,000 minutes out of 124,000, against a national NAS share of 21%.
Cancellations sit at 1.50% against a national 1.89%, which is ordinary. Diversions add another 0.70%.
Connections and stage length
What a delay here actually costs
10.0% 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 76.0% on time across 6,141 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 6,142 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 ORD 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. September runs 85.8% on time and March 68.1%, a swing of 18 points. If the dates move at all, move them out of March before you think about anything else. 6,007 completed flights over 12 months sit behind that.
Common questions
IAH to ORD questions
How often is IAH to ORD 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 24.9% of the 6,142 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on IAH to ORD?
United Airlines leads at 78.2% on time across 4,084 flights. American Airlines is at the other end on 67.3%, a gap of 11 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 IAH to ORD?
The 5am–8am departure window is the strongest at 87.9% on time. The 5pm–8pm window is the weakest at 57.3%, 31 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 March delays on IAH to ORD?
March is the weakest month at 68.1% on time, compared with 85.8% in September. Across the year that is 18 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
- ORD to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- United Airlines on IAH to ORD78.2%
- Republic Airways on IAH to ORD74.6%
- Envoy Air on IAH to ORD73.5%
- Frontier Airlines on IAH to ORD67.8%
- American Airlines on IAH to ORD67.3%
- Spirit Airlines on IAH to ORD61.7%
- IAH to DFW, a related route76.4%
- LGA to ORD, a related route66.7%
- IAH to LAX, a related route84.1%
- United Airlines on-time record78.2%
- Republic Airways on-time record74.6%
- Envoy Air on-time record73.5%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. IAH to ORD and ORD to IAH 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.