Route reliability record
DEN→GTF
Denver to Great Falls
- Flights
- 729
- Period
- July 2025 to June 2026
- Distance
- 623 mi
- Carriers
- 2
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 729 DEN to GTF flights, with a median arrival 5 minutes early.
Best time to fly DEN to GTF: a 8pm–5am departure, ideally on a Monday. Flights in that window arrived on time 94.6% of the time and Monday flights 82.7%, against 77.7% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
77.7%
Arrivals under 15 minutes late, of 725 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.81%
Best carrier
United
74.5% on time across 528 flights
These figures cover 729 flights between July 2025 and June 2026. Beyond the headline rate, 9.0% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on DEN to GTF
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 | 85.9% | 67 min | 1.00% | A |
| United Airlines | 528 | 74.5% | 65 min | 0.38% | C+ |
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 27 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–8am—
- 8am–11am—
- 11am–2pm365 flights83.7%
- 2pm–5pm—
- 5pm–8pm308 flights67.3%
- 8pm–5am56 flights94.6%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is the strongest at 94.6% on time. The full set of windows spans 27 points.
Across the year
When delays peak on this route
This route's year swings by 42 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 53.3% on time, 42 points below November, the best at 94.9%. 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, Monday is the strongest day at 82.7% on time and Wednesday the weakest at 69.9%. 13 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 52% of the 11,000 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.
- 52%Late-arriving aircraft
- 29%Carrier
- 15%National Airspace System
- 5%Extreme weather
52% 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 11,000 reported delay minutes here, that single category outweighs weather by 10 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 10,629 reported delay minutes.
Cancellations are rare at 0.55%, 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 actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.0% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 85.6% on time across 729 flights, 8 points above 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 GTF 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 77.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 725 completed flights over 12 months sit behind that.
Common questions
DEN to GTF questions
How often is DEN to GTF delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.3% of the 729 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is DEN to GTF compared with the rest of the country?
77.7% of flights arrive on time here against a national 77.6%, a difference of half a point in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on DEN to GTF?
The 8pm–5am departure window is the strongest at 94.6% on time. The 5pm–8pm window is the weakest at 67.3%, 27 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 DEN to GTF?
June is the weakest month at 53.3% on time, compared with 94.9% in November. Across the year that is 42 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
- GTF to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- SkyWest Airlines on DEN to GTF85.9%
- United Airlines on DEN to GTF74.5%
- DEN to PHX, a related route75.7%
- SLC to GTF, a related route93.2%
- DEN to SLC, a related route77.5%
- SkyWest Airlines on-time record85.9%
- United Airlines on-time record74.5%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
Direction matters. DEN to GTF and GTF to DEN 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.