Carrier route record
UABOS→DEN
United Airlines · Boston to Denver
- Flights
- 1,908
- Period
- July 2025 to June 2026
- Share of route
- 49%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on BOS to DEN 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 about an hour on average. That is a workable record, not a spotless one. That rests on 1,908 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 400 at 81.4% on time.
Set against the rest of the country, United's BOS to DEN record is 5 points better than the US average of 77.6%. That gap is worth roughly 54 fewer late arrivals for every thousand flights.
Key figures
On time
83.0%
Arrivals under 15 minutes late, of 1,882 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.00%
National rate is 1.81%
Whole route
76.5%
Every carrier on BOS to DEN, 3,899 flights
These figures cover 1,908 flights between July 2025 and June 2026. The median arrival is 9 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
United against every carrier on BOS to DEN
United flew 1,908 of the 3,899 flights on BOS to DEN, about 49% of it. Its 83.0% on time is 7 points better than the route as a whole, which runs 76.5%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 83.0% to Southwest at 64.8%.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.4% of the time; Southwest Airlines manages 64.8%. Sample sizes sit next to every figure, because a two-point gap across 910 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 1,908 | 83.0% | 64 min | 1.00% | B |
| Delta Air Lines | 400 | 81.4% | 46 min | 1.75% | B |
| JetBlue Airways | 681 | 70.9% | 60 min | 1.76% | C |
| Southwest Airlines | 910 | 64.8% | 54 min | 0.88% | D+ |
The spread between Delta and Southwest is 17 points, wide enough that it should decide the booking. On a hundred trips that is 17 more arrivals inside the on-time window.
Flight by flight
United flight numbers on BOS 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 34 points, against 17 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am364 flights91.1%
- 8am–11am278 flights92.0%
- 11am–2pm392 flights89.6%
- 2pm–5pm528 flights83.2%
- 5pm–8pm242 flights58.1%
- 8pm–5am104 flights63.5%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 58.1% on time, against 92.0% for the 8am–11am 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 2pm–5pm window is the busiest, with 528 flights scheduled in it.
Across the year
United on BOS to DEN through the year
July is the worst month at 75.8% on time, 17 points below April, the best at 92.6%. 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 192 flights.
Across the week, Tuesday is the strongest day at 87.3% on time and Thursday the weakest at 75.6%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 47% of the 20,000 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.
- 47%Late-arriving aircraft
- 28%National Airspace System
- 22%Carrier
- 3%Extreme weather
47% 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 20,000 reported delay minutes here, that single category outweighs weather by 18 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 20,387 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 92.0% on time here.
Cancellations sit at 1.00% against a national 1.81%, which is ordinary. Diversions add another 0.37%.
Connections and stage length
What a delay here costs
5.5% 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 about an hour, which a normal layover absorbs.
At 1,754 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 77.1% on time across 1,911 flights, 6 points below 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 6 points of difference.
The sample behind these figures is 1,908 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.
What to do with this
Booking United on BOS to DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 92.6% on time and July 75.8%, a swing of 17 points. If the dates move at all, move them out of July before you think about anything else. 1,882 completed flights over 12 months sit behind that.
Related
Where to go next
- BOS to DEN, every carrier
- United on DEN to BOS, the return leg
- Delta Air Lines on BOS to DEN81.4%
- JetBlue Airways on BOS to DEN70.9%
- Southwest Airlines on BOS to DEN64.8%
- United Airlines network-wide record
- Boston Logan International (BOS) delay statistics
- Denver International (DEN) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.