Route reliability record
BIL→DEN
Billings to Denver
- Flights
- 1,774
- Period
- September 2025 to August 2026
- Distance
- 455 mi
- Carriers
- 2
This route lands a B+, 5 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 an hour and a half on average. That rests on 1,774 BIL to DEN flights, of which United Airlines flew 725 at 84.1% on time.
Best time to fly BIL to DEN: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 92.6% of the time and Tuesday flights 86.1%, against 82.5% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.3%. That gap is worth roughly 52 fewer late arrivals for every thousand flights.
Key figures
On time
82.5%
Arrivals under 15 minutes late, of 1,751 completed flights
Avg delay
89 min
Across delayed arrivals only, not all flights
Cancelled
0.96%
National rate is 1.89%
Best carrier
United
84.1% on time across 725 flights
These figures cover 1,774 flights between September 2025 and August 2026. The median arrival is 12 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.
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Carrier by carrier
Which airline is most reliable on BIL 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 | 725 | 84.1% | 85 min | 0.28% | B+ |
| SkyWest Airlines | 1,049 | 81.3% | 91 min | 1.43% | B |
No carrier stands out. United tops the table at 84.1%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on BIL 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.
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Best ways to make this trip
The most reliable ways to fly Billings to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. BIL → DENBillings to Denver | United Airlines | 83.9% | 84.1% | 0.28% | 5am–8am, Sun | UA 372 07:00 |
| 2. BIL → DENBillings to Denver | SkyWest Airlines | 80.1% | 81.3% | 1.43% | 5am–8am, Sat | OO 4758 18:00 |
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 24 points, against 3 points between the best and worst carrier.
- 5am–8am584 flights92.6%
- 8am–11am268 flights92.1%
- 11am–2pm95 flights90.3%
- 2pm–5pm504 flights72.7%
- 5pm–8pm323 flights68.7%
- 8pm–5am—
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.6% of the time, against 68.7% for the evening window. That is 24 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 584 flights scheduled in it.
Explore
Filter BIL 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 BIL to DEN, the best departure window is 5am–8am at 92.6% on time and the worst is 5pm–8pm at 68.7%, a wide gap of 23.9 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am92.6%
- 8–11am92.1%
- 11am–2pm90.3%
- 2–5pm72.7%
- 5–8pm68.7%
- 8pm–5am—
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 24 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 70.2% on time, 24 points below April, the best at 93.7%. 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. July was the busiest month here, with 179 flights.
Across the week, Tuesday is the strongest day at 86.1% on time and Friday the weakest at 79.4%, a spread of 7 points.
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 27,000 reported delay minutes.
- 38%Late-arriving aircraft
- 29%Carrier
- 25%National Airspace System
- 8%Extreme weather
38% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 27,000 reported delay minutes here, that single category outweighs weather by 5 to one. The split is drawn from 27,198 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 92.6% on time here.
Cancellations sit at 0.96% against a national 1.89%, which is ordinary. Diversions add another 0.34%.
Connections and stage length
What a delay here actually costs
7.9% 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 an hour and a half, which a normal layover absorbs.
At 455 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg runs 80.3% on time across 1,774 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,774 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 93.7% on time and August 70.2%, a swing of 24 points. If the dates move at all, move them out of August before you think about anything else. 1,751 completed flights over 12 months sit behind that.
Common questions
BIL to DEN questions
How often is BIL 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 17.5% of the 1,774 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on BIL to DEN?
United Airlines leads at 84.1% on time across 725 flights. SkyWest Airlines is at the other end on 81.3%, 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 BIL to DEN?
The 5am–8am departure window is the strongest at 92.6% on time. The 5pm–8pm window is the weakest at 68.7%, 24 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 BIL to DEN?
August is the weakest month at 70.2% on time, compared with 93.7% in April. Across the year that is 24 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 BIL — the return legseparate record
- Denver International (DEN) delay statistics
- United Airlines on BIL to DEN84.1%
- SkyWest Airlines on BIL to DEN81.3%
- BIL to SLC, a related route91.3%
- PHX to DEN, a related route76.7%
- SLC to DEN, a related route79.0%
- United Airlines on-time record84.1%
- SkyWest Airlines on-time record81.3%
- 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. BIL to DEN and DEN to BIL 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.