Carrier route record

UADEN→IAD

United Airlines · Denver to Washington

Flights: 2,797
Period: July 2025 to June 2026
Share of route: 79%
Carriers: 2

Historical statistics for July 2025 to June 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 7 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 2,797 flights, with a median arrival 9 minutes early.

Set against the rest of the country, United's DEN to IAD record is 7 points better than the US average of 77.6%. That gap is worth roughly 68 fewer late arrivals for every thousand flights.

On time

84.4%

Arrivals under 15 minutes late, of 2,777 completed flights

Avg delay

70 min

Across delayed arrivals only, not all flights

Cancelled

0.46%

National rate is 1.81%

Whole route

80.3%

Every carrier on DEN to IAD, 3,558 flights

These figures cover 2,797 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 DEN to IAD

United flew 2,797 of the 3,558 flights on DEN to IAD, most of the route. Its 84.4% on time is 4 points better than the route as a whole, which runs 80.3%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 84.4% to Southwest at 65.4%.

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.

On-time performance by carrier on DEN to IAD
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)	2,797	84.4%	70 min	0.46%	B+
Southwest Airlines	761	65.4%	53 min	0.92%	C+

Flight by flight

United flight numbers on DEN to IAD

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 29 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am278 flights96.0%
8am–11am648 flights85.7%
11am–2pm546 flights84.3%
2pm–5pm549 flights85.6%
5pm–8pm434 flights66.6%
8pm–5am342 flights93.5%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 96.0% of the time, against 66.6% for the evening window. That is 29 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

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 66.3% on time, 29 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 277 flights.

Across the week, Tuesday is the strongest day at 88.3% on time and Sunday the weakest at 81.2%. 7 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 48% 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.

Late-arriving aircraft
48%
Carrier
29%
National Airspace System
20%
Extreme weather
1%
Security
1%

48% 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 30,000 reported delay minutes here, that single category outweighs weather by 34 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 30,257 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 96.0% on time here.

Cancellations are rare at 0.46%, 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

5.8% 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.

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. 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 83.2% on time across 2,798 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.

The sample behind these figures is 2,797 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 66.3%, a swing of 29 points. If the dates move at all, move them out of July before you think about anything else. 2,777 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures