Route profile
IAD→DEN
Flight reliability, delays and best times to fly from Washington to Denver, 1,452 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 67% of comparable major US routes (4,598 compared)
Calculated from 10,260 flights. How this is calculated
IAD → DEN arrives on time 81.5% of the time; the return trip, DEN → IAD, arrives on time 78.7% of the time, a 2.7-point gap between the two directions of the same city pair.
IAD → DEN spends 28.0 minutes on the ground on a 1,452-mile trip: 18.7 minutes from pushback to wheels-up at IAD and 9.3 minutes from touchdown to gate at DEN.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Every day of the week performs about the same on this route, steadier than 96% of 4,467 comparable routes.
83.5% on time on the best day (Wednesday) against 79.5% on the worst (Thursday).
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 4,467 in the comparison.
Why IAD → DEN flights are cancelled
July 2023 – July 2026
IAD → DEN cancelled 89 of 10,260 scheduled flights — about 1 in every 115. The reason filed most often was the airline, 65.2% of the cancellations coded on this route — about 1 in every 177 scheduled flights.
Share of cancellations
Of 89 cancelled departures carrying a reason code.
What each reason means
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
58 cancellations, 65.2% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
25 cancellations, 28.1% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
6 cancellations, 6.7% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. With only one or two carriers on the route, the split mostly reflects how they file. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
89 coded cancellations were recorded on IAD → DEN; the section appears from 50.
When it goes wrong
July 2023 – July 2026
37 min late
against a median of 7 min early
Percentiles over 10,260 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at DEN after arriving from IAD.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 34% | Likely to miss |
| 45 min | 18% | High risk |
| 60 min | 12% | Some risk |
| 90 min | 6.4% | Some risk |
| 120 min | 4.2% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 0.87% of the time and diverts 0.46% of the time, which a late arrival never shows up in.
Chance of missing is the share of 10,124 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 37 minutes late (90th-percentile gate arrival delay), over 10,260 operations.
Any other layover length: connection checker.
Best time to fly
IAD → DEN flights departing 5–9 AM arrived on time 89.9% of the time, against 71.2% for 6–9 PM departures, a gap of 18.7 percentage points.
By departure window
By departure hour
- 12 AM to 4 AM: too few flights to score
- 5 AM: 93.1% on time from 250 flights
- 6 AM: 94.2% on time from 488 flights
- 7 AM: 94.6% on time from 222 flights
- 8 AM: 86.4% on time from 1,135 flights
- 9 AM: 93.5% on time from 202 flights
- 10 AM: 88.9% on time from 939 flights
- 11 AM: 83.1% on time from 130 flights
- 12 PM: 89.6% on time from 1,205 flights
- 1 PM: 87.5% on time from 120 flights
- 2 PM: 80.1% on time from 698 flights
- 3 PM: 76.8% on time from 483 flights
- 4 PM: 75.1% on time from 871 flights
- 5 PM: 70.1% on time from 1,397 flights
- 6 PM: 65.8% on time from 344 flights
- 7 PM: 73.2% on time from 539 flights
- 8 PM: 74.7% on time from 241 flights
- 9 PM: too few flights to score
- 10 PM: 79.7% on time from 995 flights
- 11 PM: too few flights to score
Why IAD → DEN runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for IAD → DEN. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on IAD → DEN, at 40.5%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 89.9% of the time and 6–9 PM departures 71.2%.
How this route holds up in bad weather
July 2023 – July 2026
Bad weather raises cancellations by a similar amount at both ends of IAD to DEN: 3.1 times the normal rate at IAD and 4.0 times at DEN. Cancelled in bad weather against normal hours: IAD 3.3% against 1.0%, DEN 2.8% against 0.7%. Flights that did leave DEN in bad weather arrived on time 51.5% of the time, against 78.8% in normal hours.
Bad weather and normal hours at the airports
Scheduled departures, July 2023 – July 2026| Departures from | IAD | DEN |
|---|---|---|
| Cancelled in bad weather | 3.3% | 2.8% |
| Cancelled in normal hours | 1.0% | 0.7% |
| Arrived on time, bad weather | 69.1% | 51.5% |
| Arrived on time, normal hours | 82.7% | 78.8% |
| Departures in bad weather | 17,867 | 92,610 |
These are airport figures, not route figures: every scheduled departure from IAD and DEN, to any destination, in hours the weather report called bad.
Weather source and limits. In full: IAD, DEN, What Weather Costs Each Airport, Who Cancels More When the Weather Turns, Airports That Change Places When Weather Turns.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 7,852 | 82.0% | 0.96% | -8 min | 6.8% |
| Southwest Airlines | 2,408 | 79.6% | 0.58% | -5 min | 5.7% |
United Airlines flew 76.5% of the 10,260 flights listed.
United Airlines arrived on time 2.4 percentage points more often than Southwest Airlines on this route.
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Thursday the least, a gap of 4.0 percentage points.
By month
- Jan: 81.6%
- Feb: 81.5%
- Mar: 86.4%
- Apr: 81.6%
- May: 77.3%
- Jun: 76.2%
- Jul: 72.3%
- Aug: 77.1%
- Sep: 86.3%
- Oct: 87.7%
- Nov: 90.2%
- Dec: 85.0%
July is historically the weakest month and November the strongest, a spread of 17.9 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 62.2% from 265 flights
- August 2023: 79.0% from 277 flights
- September 2023: 84.5% from 248 flights
- October 2023: 88.8% from 250 flights
- November 2023: 87.7% from 204 flights
- December 2023: 91.5% from 234 flights
- January 2024: 76.0% from 221 flights
- February 2024: 83.1% from 201 flights
- March 2024: 89.3% from 253 flights
- April 2024: 78.4% from 262 flights
- May 2024: 71.7% from 301 flights
- June 2024: 75.8% from 290 flights
- July 2024: 78.9% from 303 flights
- August 2024: 76.2% from 296 flights
- September 2024: 89.1% from 287 flights
- October 2024: 90.7% from 283 flights
- November 2024: 91.0% from 279 flights
- December 2024: 88.1% from 273 flights
- January 2025: 80.2% from 254 flights
- February 2025: 78.9% from 230 flights
- March 2025: 89.7% from 293 flights
- April 2025: 78.2% from 292 flights
- May 2025: 74.8% from 311 flights
- June 2025: 73.2% from 327 flights
- July 2025: 68.1% from 361 flights
- August 2025: 76.2% from 335 flights
- September 2025: 85.0% from 294 flights
- October 2025: 83.7% from 283 flights
- November 2025: 91.3% from 276 flights
- December 2025: 77.1% from 304 flights
- January 2026: 87.0% from 280 flights
- February 2026: 82.4% from 257 flights
- March 2026: 80.8% from 300 flights
- April 2026: 87.9% from 291 flights
- May 2026: 85.0% from 316 flights
- June 2026: 80.5% from 263 flights
- July 2026: 80.5% from 266 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 83.0% against 81.1% in the 12 months before — improving by 1.9 percentage points.
Data and methodology
Calculated by FlyerIntel from 10,260 IAD → DEN flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed