Carrier route record
UADEN→BOS
United Airlines · Denver to Boston
- Flights
- 1,911
- 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 DEN to BOS lands a B+, level with the national rate of 77.6%. Roughly one flight in four 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 1,911 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 400 at 75.8% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on DEN to BOS from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
77.1%
Arrivals under 15 minutes late, of 1,892 completed flights
Avg delay
70 min
Across delayed arrivals only, not all flights
Cancelled
0.84%
National rate is 1.81%
Whole route
71.4%
Every carrier on DEN to BOS, 3,903 flights
These figures cover 1,911 flights between July 2025 and June 2026. Beyond the headline rate, 8.9% 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 DEN to BOS
United flew 1,911 of the 3,903 flights on DEN to BOS, about 49% of it. Its 77.1% on time is 6 points better than the route as a whole, which runs 71.4%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 77.1% to Southwest at 59.7%.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 75.8% of the time; Southwest Airlines manages 59.7%. 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) | 1,911 | 77.1% | 70 min | 0.84% | B+ |
| Delta Air Lines | 400 | 75.8% | 56 min | 1.50% | B |
| JetBlue Airways | 682 | 68.6% | 82 min | 2.05% | C |
| Southwest Airlines | 910 | 59.7% | 66 min | 1.10% | D |
The spread between Delta and Southwest is 16 points, wide enough that it should decide the booking. On a hundred trips that is 16 more arrivals inside the on-time window.
Flight by flight
United flight numbers on DEN to BOS
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 31 points, against 16 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am122 flights96.7%
- 8am–11am609 flights81.3%
- 11am–2pm2 flights—
- 2pm–5pm586 flights65.9%
- 5pm–8pm364 flights71.1%
- 8pm–5am228 flights93.8%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 96.7% of the time, against 65.9% for the afternoon window. That is 31 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 609 flights scheduled in it.
Across the year
United on DEN to BOS through the year
Delays peak in September, when the on-time rate falls to 56.6%. January is the strongest month at 89.1%. Moving a flexible trip across that boundary buys 32 points. July was the busiest month here, with 192 flights.
Across the week, Saturday is the strongest day at 85.8% on time and Monday the weakest at 72.4%. 13 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. National Airspace System accounts for 53% of the 30,000 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.
- 53%National Airspace System
- 33%Late-arriving aircraft
- 13%Carrier
- 1%Extreme weather
53% 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 16,000 minutes out of 30,000, against a national NAS share of 21%. The split is drawn from 30,364 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 96.7% on time here.
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 costs
8.9% 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 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 83.0% on time across 1,908 flights, 6 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 6 points of difference.
The sample behind these figures is 1,911 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 DEN to BOS
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 89.1% on time and September 56.6%, a swing of 32 points. If the dates move at all, move them out of September before you think about anything else. 1,892 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to BOS, every carrier
- United on BOS to DEN, the return leg
- Delta Air Lines on DEN to BOS75.8%
- JetBlue Airways on DEN to BOS68.6%
- Southwest Airlines on DEN to BOS59.7%
- United Airlines network-wide record
- Denver International (DEN) delay statistics
- Boston Logan International (BOS) 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.