Route reliability record
BIL→DEN
Billings to Denver
- Flights
- 1,782
- Period
- July 2025 to June 2026
- Distance
- 455 mi
- Carriers
- 2
This route lands a B+, 5 points better than the national rate of 77.6%. 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 is a workable record, not a spotless one. That rests on 1,782 BIL to DEN flights, of which United Airlines flew 730 at 82.7% on time.
Best time to fly BIL to DEN: a 5am–8am departure, ideally on a Sunday. Flights in that window arrived on time 92.6% of the time and Sunday flights 85.8%, against 82.3% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.6%. That gap is worth roughly 47 fewer late arrivals for every thousand flights.
Key figures
On time
82.3%
Arrivals under 15 minutes late, of 1,758 completed flights
Avg delay
76 min
Across delayed arrivals only, not all flights
Cancelled
0.84%
National rate is 1.81%
Best carrier
United
82.7% on time across 730 flights
These figures cover 1,782 flights between July 2025 and June 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.
Carrier by carrier
Which airline is most reliable on BIL to DEN
The two carriers here are closely matched: about a point 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 | 730 | 82.7% | 69 min | 0.00% | B+ |
| SkyWest Airlines | 1,052 | 81.9% | 82 min | 1.43% | B |
No carrier stands out. United tops the table at 82.7%, about a point 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.
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 | 82.7% | 82.7% | 0.00% | 5am–8am, Sun | UA 372 07:00 |
| 2. BIL → DENBillings to Denver | SkyWest Airlines | 80.7% | 81.9% | 1.43% | 5am–8am, Tue | OO 4728 10:54 |
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 23 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am584 flights92.6%
- 8am–11am255 flights90.9%
- 11am–2pm115 flights87.6%
- 2pm–5pm508 flights72.2%
- 5pm–8pm320 flights69.8%
- 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 69.8% for the evening window. That is 23 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.
Across the year
When delays peak on this route
This route's year swings by 26 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 68.2% on time, 26 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 183 flights.
Across the week, Sunday is the strongest day at 85.8% on time and Monday the weakest at 79.5%. 6 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 24,000 reported delay minutes.
- 33%Late-arriving aircraft
- 32%National Airspace System
- 27%Carrier
- 8%Extreme weather
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. The split is drawn from 23,819 reported delay minutes.
No single cause dominates. late-arriving aircraft at 33%, national airspace system at 32% and carrier at 27% split the 24,000 reported delay minutes between them. An even spread like this usually means the operation is running close to its designed capacity with no one obvious weak point, and it is the hardest pattern for a traveller to route around.
Cancellations are rare at 0.84%, 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
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.
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 79.6% on time across 1,782 flights, within 3 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 1,782 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 68.2%, a swing of 26 points. If the dates move at all, move them out of August before you think about anything else. 1,758 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 17.7% of the 1,782 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on BIL to DEN?
United Airlines leads at 82.7% on time across 730 flights. SkyWest Airlines is at the other end on 81.9%, a gap of about a point. 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 69.8%, 23 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 68.2% on time, compared with 93.7% in April. Across the year that is 26 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 DEN82.7%
- SkyWest Airlines on BIL to DEN81.9%
- BIL to SLC, a related route91.6%
- PHX to DEN, a related route77.2%
- SLC to DEN, a related route77.8%
- United Airlines on-time record82.7%
- SkyWest Airlines on-time record81.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.