Route reliability record
IAH→DEN
Houston to Denver
- Flights
- 4,728
- Period
- September 2025 to August 2026
- Distance
- 861 mi
- Carriers
- 2
This route lands a B+, 6 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 4,728 IAH to DEN flights, of which United Airlines flew 3,894 at 83.6% on time.
Best time to fly IAH to DEN: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 91.1% of the time and Tuesday flights 86.2%, against 83.0% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.3%. That gap is worth roughly 57 fewer late arrivals for every thousand flights.
Key figures
On time
83.0%
Arrivals under 15 minutes late, of 4,699 completed flights
Avg delay
69 min
Across delayed arrivals only, not all flights
Cancelled
0.40%
National rate is 1.89%
Best carrier
United
83.6% on time across 3,894 flights
These figures cover 4,728 flights between September 2025 and August 2026. The median arrival is 10 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.
Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Carrier by carrier
Which airline is most reliable on IAH to DEN
The two carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,894 | 83.6% | 67 min | 0.23% | B+ |
| Frontier Airlines | 834 | 80.2% | 76 min | 1.20% | B |
No carrier stands out. United tops the table at 83.6%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on IAH to DEN
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.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Best ways to make this trip
The most reliable ways to fly Houston to Denver
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 → DENHouston to Denver | United Airlines | 83.4% | 83.6% | 0.23% | 5am–8am, Tue | UA 1654 18:19 |
| 2. IAH → DENHouston to Denver | Frontier Airlines | 79.2% | 80.2% | 1.20% | 8am–11am, Wed | F9 3229 06:45 |
| 3. HOU → DENHouston to Denver | Southwest Airlines | 77.1% | 77.4% | 0.34% | 5am–8am, 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 25 points, against 3 points between the best and worst carrier.
- 5am–8am1,000 flights91.1%
- 8am–11am974 flights88.7%
- 11am–2pm636 flights87.2%
- 2pm–5pm779 flights73.7%
- 5pm–8pm481 flights66.5%
- 8pm–5am858 flights81.4%
Scale runs 60% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.1% of the time, against 66.5% for the evening window. That is 25 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,000 flights scheduled in it.
Explore
Filter IAH to DEN 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 DEN, the best departure window is 5am–8am at 91.1% on time and the worst is 5pm–8pm at 66.5%, a wide gap of 24.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.1%
- 8–11am88.7%
- 11am–2pm87.2%
- 2–5pm73.7%
- 5–8pm66.5%
- 8pm–5am81.4%
best all US flightsScale 60% 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 71.7% on time, 16 points below April, the best at 87.8%. 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. July was the busiest month here, with 444 flights.
Across the week, Tuesday is the strongest day at 86.2% on time and Saturday the weakest at 81.1%, a spread of 5 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 42% of the 55,000 delay minutes carriers reported here, and the remaining four split what is left.
- 42%Late-arriving aircraft
- 27%National Airspace System
- 26%Carrier
- 5%Extreme weather
42% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 55,000 reported delay minutes here, that single category outweighs weather by 9 to one. The split is drawn from 55,050 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 91.1% on time here.
Cancellations are rare at 0.40%, below the national 1.89% 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 actually costs
6.2% of arrivals land an hour or more late, close to the national 8.3%, so 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.
The return leg is a different operation and performs like one: it runs 79.6% on time across 4,728 flights, 3 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 3 points of difference.
The sample behind these figures is 4,728 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 DEN 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. April runs 87.8% on time and June 71.7%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 4,699 completed flights over 12 months sit behind that.
Common questions
IAH to DEN questions
How often is IAH to DEN delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.0% of the 4,728 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 IAH to DEN?
United Airlines leads at 83.6% on time across 3,894 flights. Frontier Airlines is at the other end on 80.2%, a gap of 3 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 DEN?
The 5am–8am departure window is the strongest at 91.1% on time. The 5pm–8pm window is the weakest at 66.5%, 25 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 IAH to DEN?
June is the weakest month at 71.7% on time, compared with 87.8% in April. 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
- DEN to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on IAH to DEN83.6%
- Frontier Airlines on IAH to DEN80.2%
- IAH to ORD, a related route75.1%
- PHX to DEN, a related route76.7%
- IAH to DFW, a related route76.4%
- United Airlines on-time record83.6%
- Frontier Airlines on-time record80.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. IAH to DEN and DEN to IAH are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Embed IAH to DEN’s on-time badge on your site
Paste this into a web page. The badge shows the current on-time rate, cancellation rate and grade, and updates every month. Preview it, or build a badge for another route or airport.
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.