Route reliability record
DEN→BOS
Denver to Boston
- Flights
- 3,851
- Period
- September 2025 to August 2026
- Distance
- 1,754 mi
- Carriers
- 4
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 3,851 DEN to BOS flights, of which United Airlines flew 1,887 at 76.8% on time.
Best time to fly DEN to BOS: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 96.8% of the time and Saturday flights 76.9%, against 69.6% for the route overall.
United Airlines is the most reliable of the four carriers covered here at 76.8% on time across 1,887 flights.
Key figures
On time
69.6%
Arrivals under 15 minutes late, of 3,782 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
1.45%
National rate is 1.89%
Best carrier
United
76.8% on time across 1,887 flights
These figures cover 3,851 flights between September 2025 and August 2026. Beyond the headline rate, 12.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on DEN to BOS
The choice of carrier is not cosmetic here. United Airlines arrives on time 76.8% of the time; Southwest Airlines manages 57.4%. Sample sizes sit next to every figure, because a two-point gap across 908 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,887 | 76.8% | 75 min | 0.95% | B+ |
| Delta Air Lines | 365 | 71.7% | 61 min | 1.10% | C |
| JetBlue Airways | 691 | 64.6% | 84 min | 3.47% | D− |
| Southwest Airlines | 908 | 57.4% | 66 min | 1.10% | D |
JetBlue Airways cancels 3.5% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Flight by flight
Flights on DEN to BOS
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 Boston
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 → BOSDenver to Boston | United Airlines | 76.1% | 76.8% | 0.95% | 5am–8am, Sat | UA 558 07:45 |
| 2. DEN → BOSDenver to Boston | Delta Air Lines | 70.9% | 71.7% | 1.10% | 11am–2pm, Sat | DL 499 11:33 |
| 3. DEN → BOSDenver to Boston | JetBlue Airways | 62.4% | 64.6% | 3.47% | 8pm–5am, Wed | B6 994 23:37 |
| 4. DEN → BOSDenver to Boston | Southwest Airlines | 56.8% | 57.4% | 1.10% | 8am–11am, Sat | — |
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 38 points, against 19 points between the best and worst carrier.
- 5am–8am158 flights96.8%
- 8am–11am956 flights76.2%
- 11am–2pm656 flights66.7%
- 2pm–5pm881 flights62.6%
- 5pm–8pm690 flights59.2%
- 8pm–5am510 flights78.4%
Scale runs 50% to 100%.
The 5pm–8pm window is where this operation falls apart: 59.2% on time, against 96.8% 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 8am–11am window is the busiest, with 956 flights scheduled in it.
Explore
Filter DEN to BOS 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 BOS, the best departure window is 5am–8am at 96.8% on time and the worst is 5pm–8pm at 59.2%, a wide gap of 37.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am96.8%
- 8–11am76.2%
- 11am–2pm66.7%
- 2–5pm62.6%
- 5–8pm59.2%
- 8pm–5am78.4%
best all US flightsScale 50% to 100%.
Across the year
When delays peak on this route
This route's year swings by 34 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.
Delays peak in September, when the on-time rate falls to 51.4%. December is the strongest month at 85.7%. Moving a flexible trip across that boundary buys 34 points. July was the busiest month here, with 396 flights.
Across the week, Saturday is the strongest day at 76.9% on time and Monday the weakest at 64.8%, a spread of 12 points.
Delay causes
Why this route gets delayed
National Airspace System accounts for 42% of the 84,000 delay minutes carriers reported here, and the remaining four split what is left.
- 42%National Airspace System
- 37%Late-arriving aircraft
- 20%Carrier
- 1%Extreme weather
- 0%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 84,000 reported delay minutes here, that single category outweighs weather by 37 to one. The split is drawn from 83,520 reported delay minutes.
42% 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 35,000 minutes out of 84,000, against a national NAS share of 21%.
Cancellations sit at 1.45% against a national 1.89%, which is ordinary. Diversions add another 0.34%.
Connections and stage length
What a delay here actually costs
12.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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 75.7% on time across 3,847 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 3,851 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 BOS 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. December runs 85.7% on time and September 51.4%, a swing of 34 points. If the dates move at all, move them out of September before you think about anything else. 3,782 completed flights over 12 months sit behind that.
Common questions
DEN to BOS questions
How often is DEN to BOS delayed?
Roughly one flight in three arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 30.4% of the 3,851 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on DEN to BOS?
United Airlines leads at 76.8% on time across 1,887 flights. Southwest Airlines is at the other end on 57.4%, a gap of 19 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 BOS?
The 5am–8am departure window is the strongest at 96.8% on time. The 5pm–8pm window is the weakest at 59.2%, 38 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 September delays on DEN to BOS?
September is the weakest month at 51.4% on time, compared with 85.7% in December. Across the year that is 34 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
- BOS to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- Boston Logan International (BOS) delay statistics
- United Airlines on DEN to BOS76.8%
- Delta Air Lines on DEN to BOS71.7%
- JetBlue Airways on DEN to BOS64.6%
- Southwest Airlines on DEN to BOS57.4%
- DEN to PHX, a related route75.6%
- DCA to BOS, a related route70.1%
- DEN to SLC, a related route78.2%
- United Airlines on-time record76.8%
- Delta Air Lines on-time record71.7%
- JetBlue Airways on-time record64.6%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. DEN to BOS and BOS 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.