Carrier route record
UAIAH→DEN
United Airlines · Houston to Denver
- Flights
- 3,875
- Period
- July 2025 to June 2026
- Share of route
- 83%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on IAH to DEN lands a B+, 4 points better than 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 3,875 flights, with a median arrival 9 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate United on IAH to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.5%
Arrivals under 15 minutes late, of 3,856 completed flights
Avg delay
69 min
Across delayed arrivals only, not all flights
Cancelled
0.21%
National rate is 1.81%
Whole route
81.2%
Every carrier on IAH to DEN, 4,673 flights
These figures cover 3,875 flights between July 2025 and June 2026. The median arrival is 9 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 DEN
United flew 3,875 of the 4,673 flights on IAH to DEN, most of the route. Its 81.5% on time is about level with the route as a whole at 81.2%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 81.5% to Frontier at 79.8%.
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) | 3,875 | 81.5% | 69 min | 0.21% | B+ |
| Frontier Airlines | 798 | 79.8% | 78 min | 0.38% | B+ |
Flight by flight
United flight numbers on IAH to DEN
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 29 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–8am600 flights92.7%
- 8am–11am842 flights87.0%
- 11am–2pm618 flights86.8%
- 2pm–5pm728 flights70.7%
- 5pm–8pm365 flights63.9%
- 8pm–5am722 flights80.7%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 63.9% on time, against 92.7% 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 8am–11am window is the busiest, with 842 flights scheduled in it.
Across the year
United on IAH to DEN through the year
July is the worst month at 71.3% on time, 16 points below April, the best at 87.7%. 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. June was the busiest month here, with 351 flights.
Across the week, Tuesday is the strongest day at 85.1% on time and Friday the weakest at 79.5%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
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 49,000 reported delay minutes.
- 37%Late-arriving aircraft
- 28%Carrier
- 27%National Airspace System
- 7%Extreme weather
37% 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 49,000 reported delay minutes here, that single category outweighs weather by 5 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 49,130 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 92.7% on time here.
Cancellations are rare at 0.21%, 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
7.1% 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 861 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 is a different operation and performs like one: it runs 78.0% on time across 3,875 flights, 4 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 4 points of difference.
The sample behind these figures is 3,875 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 DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 87.7% on time and July 71.3%, a swing of 16 points. If the dates move at all, move them out of July before you think about anything else. 3,856 completed flights over 12 months sit behind that.
Related
Where to go next
- IAH to DEN, every carrier
- United on DEN to IAH, the return leg
- Frontier Airlines on IAH to DEN79.8%
- United Airlines network-wide record
- George Bush Intercontinental (IAH) delay statistics
- Denver International (DEN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.