Route reliability record
GTF→DEN
Great Falls to Denver
- Flights
- 729
- Period
- July 2025 to June 2026
- Distance
- 623 mi
- Carriers
- 2
This route earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 729 GTF to DEN flights, with a median arrival 16 minutes early.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.6%. That gap is worth roughly 80 fewer late arrivals for every thousand flights.
Key figures
On time
85.6%
Arrivals under 15 minutes late, of 720 completed flights
Avg delay
92 min
Across delayed arrivals only, not all flights
Cancelled
0.96%
National rate is 1.81%
Best carrier
United
83.3% on time across 528 flights
These figures cover 729 flights between July 2025 and June 2026. The median arrival is 16 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
Which airline is most reliable on GTF to DEN
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 |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 201 | 91.5% | 121 min | 1.00% | A |
| United Airlines | 528 | 83.3% | 86 min | 0.95% | B+ |
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 15 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–8am365 flights92.8%
- 8am–11am—
- 11am–2pm—
- 2pm–5pm364 flights78.3%
- 5pm–8pm—
- 8pm–5am—
Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.8% of the time, against 78.3% for the afternoon window. That is 15 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 365 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 21 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.
August is the worst month at 72.1% on time, 21 points below February, the best at 92.7%. 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. January was the busiest month here, with 62 flights.
Across the week, Sunday is the strongest day at 90.3% on time and Friday the weakest at 78.8%. 12 points is a smaller lever than departure hour, but it is free.
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 9,527 reported delay minutes.
- 30%National Airspace System
- 25%Extreme weather
- 23%Carrier
- 22%Late-arriving aircraft
Extreme weather accounts for 25% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 4.0 times the usual weather exposure. The split is drawn from 9,527 reported delay minutes.
Cancellations sit at 0.96% against a national 1.81%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here actually costs
6.5% 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 an hour and a half, which a normal layover absorbs.
The 623 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 77.7% on time across 729 flights, 8 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 8 points of difference.
One caution: this is a thin sample. 729 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.
Work out the risk of missing a connection in DEN after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 729 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 85.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 720 completed flights over 12 months sit behind that.
Common questions
GTF to DEN questions
How often is GTF to DEN delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 14.4% of the 729 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
How reliable is GTF to DEN compared with the rest of the country?
85.6% of flights arrive on time here against a national 77.6%, a difference of 8 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on GTF to DEN?
The 5am–8am departure window is the strongest at 92.8% on time. The 2pm–5pm window is the weakest at 78.3%, 15 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 August delays on GTF to DEN?
August is the weakest month at 72.1% on time, compared with 92.7% in February. Across the year that is 21 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 GTF — the return legseparate record
- Denver International (DEN) delay statistics
- SkyWest Airlines on GTF to DEN91.5%
- United Airlines on GTF to DEN83.3%
- GTF to SLC, a related route92.3%
- PHX to DEN, a related route77.2%
- SLC to DEN, a related route77.8%
- SkyWest Airlines on-time record91.5%
- United Airlines on-time record83.3%
- 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
Direction matters. GTF to DEN and DEN to GTF 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.