Carrier route record
UABOI→DEN
United Airlines · Boise to Denver
- Flights
- 946
- Period
- July 2025 to June 2026
- Share of route
- 31%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on BOI to DEN lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 946 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 871 at 85.8% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on BOI to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.1%
Arrivals under 15 minutes late, of 937 completed flights
Avg delay
89 min
Across delayed arrivals only, not all flights
Cancelled
0.53%
National rate is 1.81%
Whole route
80.9%
Every carrier on BOI to DEN, 3,035 flights
These figures cover 946 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% 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
United against every carrier on BOI to DEN
United flew 946 of the 3,035 flights on BOI to DEN, about 31% of it. Its 80.1% on time is about level with the route as a whole at 80.9%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from SkyWest at 85.8% to Southwest at 77.8%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 85.8% of the time; Southwest Airlines manages 77.8%. Sample sizes sit next to every figure, because a two-point gap across 1,092 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 871 | 85.8% | 86 min | 0.00% | A+ |
| Frontier Airlinesthin sample | 126 | 80.2% | 141 min | 0.00% | B+ |
| United Airlines (this page) | 946 | 80.1% | 89 min | 0.53% | B+ |
| Southwest Airlines | 1,092 | 77.8% | 56 min | 0.09% | B+ |
SkyWest leads Southwest by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
United flight numbers on BOI to DEN
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 54 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am364 flights91.7%
- 8am–11am128 flights91.3%
- 11am–2pm—
- 2pm–5pm364 flights75.3%
- 5pm–8pm90 flights37.8%
- 8pm–5am—
Scale runs 30% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 37.8% on time, against 91.7% 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 5am–8am window is the busiest, with 364 flights scheduled in it.
Across the year
United on BOI to DEN through the year
July is the worst month at 65.5% on time, 26 points below February, the best at 91.1%. 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 123 flights.
Across the week, Tuesday is the strongest day at 87.3% on time and Friday the weakest at 73.0%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
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 17,000 reported delay minutes.
- 39%Carrier
- 34%National Airspace System
- 23%Late-arriving aircraft
- 5%Extreme weather
34% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 5,662 minutes out of 17,000, against a national NAS share of 21%. The split is drawn from 16,589 reported delay minutes.
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 6,403 of the 17,000 delay minutes reported here.
Cancellations are rare at 0.53%, 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 costs
8.6% 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 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. 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 runs 79.2% on time across 946 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 946 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.
What to do with this
Booking United on BOI to DEN
Put together: treat all of this as provisional. 946 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 80.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 937 completed flights over 12 months sit behind that.
Related
Where to go next
- BOI to DEN, every carrier
- United on DEN to BOI, the return leg
- SkyWest Airlines on BOI to DEN85.8%
- Frontier Airlines on BOI to DEN80.2%
- Southwest Airlines on BOI to DEN77.8%
- United Airlines network-wide record
- Denver International (DEN) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- Connecting flights: how much buffer the data says you need
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.