Route reliability record
DEN→BOI
Denver to Boise
- Flights
- 3,038
- Period
- September 2025 to August 2026
- Distance
- 649 mi
- Carriers
- 4
This route lands a B+, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 3,038 DEN to BOI flights, of which SkyWest Airlines flew 898 at 80.7% on time.
Best time to fly DEN to BOI: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 93.2% of the time and Tuesday flights 82.3%, against 76.3% for the route overall.
SkyWest Airlines is the most reliable of the three carriers covered here at 80.7% on time across 898 flights.
Key figures
On time
76.3%
Arrivals under 15 minutes late, of 3,025 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.10%
National rate is 1.89%
Best carrier
SkyWest
80.7% on time across 898 flights
These figures cover 3,038 flights between September 2025 and August 2026. The median arrival is 2 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 DEN to BOI
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 80.7% of the time; Southwest Airlines manages 71.8%. Sample sizes sit next to every figure, because a two-point gap across 1,089 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlinesthin sample | 132 | 81.1% | 34 min | 0.00% | B+ |
| SkyWest Airlines | 898 | 80.7% | 69 min | 0.22% | B+ |
| United Airlines | 919 | 76.8% | 60 min | 0.00% | B+ |
| Southwest Airlines | 1,089 | 71.8% | 47 min | 0.09% | C+ |
SkyWest leads Southwest by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on DEN to BOI
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 Denver to Boise
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. DEN → BOIDenver to Boise | SkyWest Airlines | 80.5% | 80.7% | 0.22% | 5am–8am, Wed | OO 5923 20:25 |
| 2. DEN → BOIDenver to Boise | United Airlines | 76.8% | 76.8% | 0.00% | 5am–8am, Tue | UA 2014 19:25 |
| 3. DEN → BOIDenver to Boise | Southwest Airlines | 71.7% | 71.8% | 0.09% | 5am–8am, Wed | — |
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 29 points, against 9 points between the best and worst carrier.
- 5am–8am369 flights93.2%
- 8am–11am487 flights85.8%
- 11am–2pm549 flights79.3%
- 2pm–5pm541 flights73.1%
- 5pm–8pm453 flights69.8%
- 8pm–5am639 flights64.2%
Scale runs 55% to 100%.
The 8pm–5am window is where this operation falls apart: 64.2% on time, against 93.2% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8pm–5am window is the busiest, with 639 flights scheduled in it.
Explore
Filter DEN to BOI 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 DEN to BOI, the best departure window is 5am–8am at 93.2% on time and the worst is 8pm–5am at 64.2%, a wide gap of 29.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am93.2%
- 8–11am85.8%
- 11am–2pm79.3%
- 2–5pm73.1%
- 5–8pm69.8%
- 8pm–5am64.2%
best all US flightsScale 55% to 100%.
Across the year
When delays peak on this route
This route's year swings by 29 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 59.3% on time, 29 points below November, the best at 88.3%. 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 261 flights.
Across the week, Tuesday is the strongest day at 82.3% on time and Friday the weakest at 70.1%, a spread of 12 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 52% of the 40,000 delay minutes carriers reported here, and the remaining four split what is left.
- 52%Late-arriving aircraft
- 30%Carrier
- 15%National Airspace System
- 2%Extreme weather
52% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 40,000 reported delay minutes here, that single category outweighs weather by 22 to one. The split is drawn from 39,732 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 93.2% on time here.
Cancellations are rare at 0.10%, below the national 1.89% 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
6.6% 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 about an hour, which a normal layover absorbs.
The 649 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.
The return leg is a different operation and performs like one: it runs 81.7% on time across 3,034 flights, 5 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 5 points of difference.
The sample behind these figures is 3,038 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 BOI 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. November runs 88.3% on time and June 59.3%, a swing of 29 points. If the dates move at all, move them out of June before you think about anything else. 3,025 completed flights over 12 months sit behind that.
Common questions
DEN to BOI questions
How often is DEN to BOI delayed?
About 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 23.7% of the 3,038 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DEN to BOI?
SkyWest Airlines leads at 80.7% on time across 898 flights. Southwest Airlines is at the other end on 71.8%, a gap of 9 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 DEN to BOI?
The 5am–8am departure window is the strongest at 93.2% on time. The 8pm–5am window is the weakest at 64.2%, 29 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 BOI?
June is the weakest month at 59.3% on time, compared with 88.3% in November. Across the year that is 29 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
- BOI to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- Frontier Airlines on DEN to BOI81.1%
- SkyWest Airlines on DEN to BOI80.7%
- United Airlines on DEN to BOI76.8%
- Southwest Airlines on DEN to BOI71.8%
- DEN to PHX, a related route75.6%
- SEA to BOI, a related route86.3%
- DEN to SLC, a related route78.2%
- Frontier Airlines on-time record81.1%
- SkyWest Airlines on-time record80.7%
- United Airlines on-time record76.8%
- 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. DEN to BOI and BOI 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.