Carrier route record
F9IAH→DEN
Frontier Airlines · Houston to Denver
- Flights
- 798
- Period
- July 2025 to June 2026
- Share of route
- 17%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.
Frontier on IAH to DEN lands a B+, 2 points better than the national rate of 77.6%. About 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 798 flights, with a median arrival 10 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate Frontier 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
79.8%
Arrivals under 15 minutes late, of 794 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
0.38%
National rate is 1.81%
Whole route
81.2%
Every carrier on IAH to DEN, 4,673 flights
These figures cover 798 flights between July 2025 and June 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.
Carrier by carrier
Frontier against every carrier on IAH to DEN
Frontier flew 798 of the 4,673 flights on IAH to DEN, about 17% of it. Its 79.8% on time is about level with the route as a whole at 81.2%. Ranked by on-time rate it is last 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 | 3,875 | 81.5% | 69 min | 0.21% | B+ |
| Frontier Airlines (this page) | 798 | 79.8% | 78 min | 0.38% | B+ |
Flight by flight
Frontier flight numbers on IAH to DEN
Departure window
When Frontier runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 22 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–8am350 flights87.1%
- 8am–11am66 flights90.8%
- 11am–2pm70 flights71.4%
- 2pm–5pm55 flights75.9%
- 5pm–8pm68 flights68.7%
- 8pm–5am189 flights70.9%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 90.8% of the time, against 68.7% for the evening window. That is 22 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 350 flights scheduled in it.
Across the year
Frontier on IAH to DEN through the year
June is the worst month at 64.6% on time, 25 points below January, the best at 89.7%. 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. May was the busiest month here, with 80 flights.
Across the week, Wednesday is the strongest day at 86.1% on time and Monday the weakest at 75.0%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Frontier runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 12,000 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.
- 45%Late-arriving aircraft
- 34%Carrier
- 19%National Airspace System
- 3%Extreme weather
45% 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 12,000 reported delay minutes here, that single category outweighs weather by 17 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 12,395 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.8% on time here.
Cancellations are rare at 0.38%, 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
7.2% 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 runs 79.0% on time across 798 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.
One caution: this is a thin sample. 798 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Frontier on IAH to DEN
Put together: treat all of this as provisional. 798 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 79.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 794 completed flights over 12 months sit behind that.
Related
Where to go next
- IAH to DEN, every carrier
- Frontier on DEN to IAH, the return leg
- United Airlines on IAH to DEN81.5%
- Frontier 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.