Route reliability record
DCA→DEN
Washington to Denver
- Flights
- 1,349
- Period
- July 2025 to June 2026
- Distance
- 1,476 mi
- Carriers
- 2
This route lands a B+, about a point better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 1,349 DCA to DEN flights, of which United Airlines flew 365 at 78.8% on time.
Best time to fly DCA to DEN: a 11am–2pm departure, ideally on a Saturday. Flights in that window arrived on time 93.2% of the time and Saturday flights 88.2%, against 78.5% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
78.5%
Arrivals under 15 minutes late, of 1,333 completed flights
Avg delay
86 min
Across delayed arrivals only, not all flights
Cancelled
0.74%
National rate is 1.81%
Best carrier
United
78.8% on time across 365 flights
These figures cover 1,349 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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
Which airline is most reliable on DCA to DEN
The two carriers here are closely matched: half a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 365 | 78.8% | 104 min | 0.27% | B+ |
| Frontier Airlines | 984 | 78.4% | 80 min | 0.91% | B+ |
No carrier stands out. United tops the table at 78.8%, half a point clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on DCA to DEN
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.
Best ways to make this trip
The most reliable ways to fly Washington to Denver
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. BWI → DENBaltimore to Denver | United Airlines | 85.1% | 85.6% | 0.55% | 8am–11am, Tue | UA 2412 08:30 |
| 2. IAD → DENWashington to Denver | United Airlines | 82.8% | 83.2% | 0.46% | 5am–8am, Tue | UA 1587 12:35 |
| 3. DCA → DENWashington to Denver | United Airlines | 78.6% | 78.8% | 0.27% | 2pm–5pm, Sat | UA 746 16:11 |
| 4. DCA → DENWashington to Denver | Frontier Airlines | 77.7% | 78.4% | 0.91% | 11am–2pm, Sat | F9 685 07:00 |
| 5. IAD → DENWashington to Denver | Southwest Airlines | 75.3% | 76.2% | 1.18% | 5am–8am, 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 28 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–8am190 flights84.1%
- 8am–11am170 flights85.7%
- 11am–2pm119 flights93.2%
- 2pm–5pm565 flights78.6%
- 5pm–8pm305 flights65.1%
- 8pm–5am—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 93.2% on time, ahead of 5pm–8pm at 65.1%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 2pm–5pm window is the busiest, with 565 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 18 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.
July is the worst month at 69.7% on time, 18 points below October, the best at 87.7%. 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. January was the busiest month here, with 116 flights.
Across the week, Saturday is the strongest day at 88.2% on time and Thursday the weakest at 72.6%. 16 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 25,000 reported delay minutes.
- 33%National Airspace System
- 29%Late-arriving aircraft
- 26%Carrier
- 12%Extreme weather
Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 1.9 times the usual weather exposure. The split is drawn from 24,690 reported delay minutes.
33% 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 8,187 minutes out of 25,000, against a national NAS share of 21%.
Cancellations are rare at 0.74%, 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 actually costs
8.2% 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 an hour and a half, which a normal layover absorbs.
The 1,476 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 81.2% on time across 1,351 flights, within 3 points 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 1,349 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 DEN 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. October runs 87.7% on time and July 69.7%, a swing of 18 points. If the dates move at all, move them out of July before you think about anything else. 1,333 completed flights over 12 months sit behind that.
Common questions
DCA to DEN questions
How often is DCA to DEN delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.5% of the 1,349 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on DCA to DEN?
United Airlines leads at 78.8% on time across 365 flights. Frontier Airlines is at the other end on 78.4%, a gap of half a point. 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 DCA to DEN?
The 11am–2pm departure window is the strongest at 93.2% on time. The 5pm–8pm window is the weakest at 65.1%, 28 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 July delays on DCA to DEN?
July is the weakest month at 69.7% on time, compared with 87.7% in October. Across the year that is 18 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
- DEN to DCA — the return legseparate record
- Ronald Reagan Washington National (DCA) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on DCA to DEN78.8%
- Frontier Airlines on DCA to DEN78.4%
- DCA to BOS, a related route71.4%
- PHX to DEN, a related route77.2%
- DCA to ORD, a related route74.3%
- United Airlines on-time record78.8%
- Frontier Airlines on-time record78.4%
- The best time of day to fly, according to 7.04 million flight records
- Connecting flights: how much buffer the data says you need
Direction matters. DCA to DEN and DEN to DCA 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.