Carrier route record
UADEN→IAD
United Airlines · Denver to Washington
- Flights
- 2,790
- Period
- September 2025 to August 2026
- Share of route
- 82%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on DEN to IAD earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 2,790 flights, with a median arrival 9 minutes early.
Set against the rest of the country, United's DEN to IAD record is 8 points better than the US average of 77.3%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.
Key figures
On time
84.8%
Arrivals under 15 minutes late, of 2,775 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
0.50%
National rate is 1.89%
Whole route
81.8%
Every carrier on DEN to IAD, 3,385 flights
These figures cover 2,790 flights between September 2025 and August 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.
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Carrier by carrier
United against every carrier on DEN to IAD
United flew 2,790 of the 3,385 flights on DEN to IAD, most of the route. Its 84.8% on time is 3 points better than the route as a whole, which runs 81.8%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 84.8% to Southwest at 67.7%.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 2,790 | 84.8% | 66 min | 0.50% | B+ |
| Southwest Airlines | 595 | 67.7% | 47 min | 1.01% | C |
Flight by flight
United flight numbers on DEN to IAD
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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 24 points, against half a point between the best and worst carrier.
- 5am–8am282 flights94.3%
- 8am–11am648 flights86.3%
- 11am–2pm497 flights84.2%
- 2pm–5pm598 flights84.2%
- 5pm–8pm422 flights70.3%
- 8pm–5am343 flights93.8%
Scale runs 60% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.3% of the time, against 70.3% for the evening window. That is 24 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 648 flights scheduled in it.
Across the year
United on DEN to IAD through the year
July is the worst month at 70.5% on time, 24 points below April, the best at 94.8%. 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 266 flights.
Across the week, Wednesday is the strongest day at 89.0% on time and Sunday the weakest at 79.7%, a spread of 9 points.
Arrival by arrival
How late United on DEN to IAD runs when it is late
United on DEN to IAD often beats the schedule: 939 of 2,775 completed flights, 34%, arrived 15 minutes or more early. The 421 late arrivals split 150 under half an hour, 126 between 30 and 60 minutes, and 145 an hour or more.
- 15+ min early939 flights33.8%
- Within 15 min1,415 flights51.0%
- 15–29 min late150 flights5.4%
- 30–59 min late126 flights4.5%
- 1–2 hours late91 flights3.3%
- 2+ hours late54 flights1.9%
Scale runs 0% to 100%.
Share of 2,775 completed flights by arrival against schedule.
113 of 397 late departures made up the time and arrived on time, 28% of them. 137 flights left on time and still arrived late.
The worst days
Worst days for United on DEN to IAD
The latest arrival of the period was on 17 February 2026, 11 hours 32 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 February 2026 | 11 hours 32 minutes | Carrier |
| 6 March 2026 | 8 hours 50 minutes | Carrier |
| 27 July 2026 | 8 hours 1 minute | Carrier |
| 8 June 2026 | 7 hours 21 minutes | Carrier |
| 17 February 2026 | 6 hours 26 minutes | Carrier |
Delay causes
Why United runs late on this route
Late-arriving aircraft accounts for 43% of the 28,000 delay minutes carriers reported here, and the remaining four split what is left.
- 43%Late-arriving aircraft
- 31%Carrier
- 23%National Airspace System
- 1%Security
- 1%Extreme weather
43% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 28,000 reported delay minutes here, that single category outweighs weather by 39 to one. The split is drawn from 27,666 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 94.3% on time here.
Cancellations are rare at 0.50%, 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 costs
5.2% 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 1,452 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 runs 84.1% on time across 2,791 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 2,790 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 IAD
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 94.8% on time and July 70.5%, a swing of 24 points. If the dates move at all, move them out of July before you think about anything else. 2,775 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to IAD, every carrier
- United on IAD to DEN, the return leg
- Southwest Airlines on DEN to IAD67.7%
- United Airlines network-wide record
- Denver International (DEN) delay statistics
- Washington Dulles International (IAD) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.