Carrier route record
UAIAH→ORD
United Airlines · Houston to Chicago
- Flights
- 4,007
- Period
- July 2025 to June 2026
- Share of route
- 66%
- Carriers
- 8
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on IAH to ORD lands a B+, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 4,007 flights, with a median arrival 5 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate United on IAH to ORD from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
78.2%
Arrivals under 15 minutes late, of 3,960 completed flights
Avg delay
70 min
Across delayed arrivals only, not all flights
Cancelled
0.60%
National rate is 1.81%
Whole route
74.8%
Every carrier on IAH to ORD, 6,080 flights
These figures cover 4,007 flights between July 2025 and June 2026. The median arrival is 5 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
United against every carrier on IAH to ORD
United flew 4,007 of the 6,080 flights on IAH to ORD, most of the route. Its 78.2% on time is 3 points better than the route as a whole, which runs 74.8%. Ranked by on-time rate it is first of eight carriers on the route, where the range runs from United at 78.2% to PSA at 50.0%. Six of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 4,007 | 78.2% | 70 min | 0.60% | B+ |
| Envoy Airthin sample | 359 | 72.8% | 62 min | 1.11% | C |
| Republic Airwaysthin sample | 357 | 71.7% | 80 min | 3.64% | C− |
| American Airlines | 798 | 67.1% | 122 min | 3.51% | C− |
| Spirit Airlinesthin sample | 305 | 66.0% | 70 min | 4.59% | C− |
| Frontier Airlinesthin sample | 248 | 61.8% | 130 min | 2.82% | D |
| SkyWest Airlinesthin sample | 2 | 50.0% | 38 min | 0.00% | F+ |
| PSA Airlinesthin sample | 4 | 50.0% | 156 min | 0.00% | F+ |
Flight by flight
United flight numbers on IAH to ORD
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 31 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,038 flights90.3%
- 8am–11am730 flights87.7%
- 11am–2pm407 flights75.1%
- 2pm–5pm385 flights72.2%
- 5pm–8pm726 flights59.3%
- 8pm–5am721 flights75.0%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 59.3% on time, against 90.3% 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 1,038 flights scheduled in it.
Across the year
United on IAH to ORD through the year
July is the worst month at 69.2% on time, 20 points below September, the best at 88.8%. 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. May was the busiest month here, with 353 flights.
Across the week, Thursday is the strongest day at 81.2% on time and Sunday the weakest at 73.0%. 8 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. National Airspace System accounts for 48% of the 60,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 48%National Airspace System
- 26%Late-arriving aircraft
- 22%Carrier
- 4%Extreme weather
48% 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 29,000 minutes out of 60,000, against a national NAS share of 21%. The split is drawn from 60,234 reported delay minutes.
Cancellations are rare at 0.60%, below the national 1.81% 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.
Connections and stage length
What a delay here costs
7.9% 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 last a little over an hour, which a normal layover absorbs.
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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 78.6% on time across 4,000 flights, within half 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 4,007 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.
What to do with this
Booking United on IAH to ORD
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 88.8% on time and July 69.2%, a swing of 20 points. If the dates move at all, move them out of July before you think about anything else. 3,960 completed flights over 12 months sit behind that.
Related
Where to go next
- IAH to ORD, every carrier
- United on ORD to IAH, the return leg
- Envoy Air on IAH to ORD72.8%
- Republic Airways on IAH to ORD71.7%
- American Airlines on IAH to ORD67.1%
- Spirit Airlines on IAH to ORD66.0%
- Frontier Airlines on IAH to ORD61.8%
- United Airlines network-wide record
- George Bush Intercontinental (IAH) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
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.