Best Time to Fly IAD to DEN: On-Time Stats by Hour & Airline
Washington Dulles International → Denver International
Data through July 2026 · Last updated October 18, 2026
3,465 flights were scheduled from Washington (IAD) to Denver (DEN) in the last 12 months, and 83.0% of those that flew arrived on time, 5.4 points above the US average of 77.6%.
Among 2 airlines, United Airlines led with 84.3% on time and Southwest Airlines was last with 77.7%.
Over 24 months, Monday was the most reliable day (84% on time) and July the worst month (73%).
The cancellation rate was 0.6% (US average 1.8%).
IAD to DEN on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| United Airlines | 84.3% | 68 min | 0.5% | 2,787 |
| Southwest Airlines | 77.7% | 51 min | 0.9% | 678 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly IAD to DEN
On-time arrival % by scheduled departure hour (local time), 6,951 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 5am–6am | 92.0% | 0.9% | 215 |
| 6am–7am | 92.9% | 0.3% | 368 |
| 7am–8am | 95.4% | 0.5% | 197 |
| 8am–9am | 86.3% | 1.2% | 739 |
| 9am–10am | 93.5% | 0.5% | 202 |
| 10am–11am | 90.2% | 0.5% | 563 |
| 11am–12pm | 82.9% | 0.0% | 41 |
| 12pm–1pm | 89.9% | 0.3% | 699 |
| 1pm–2pm | 90.7% | 0.0% | 75 |
| 2pm–3pm | 81.1% | 0.5% | 580 |
| 3pm–4pm | 75.5% | 0.0% | 383 |
| 4pm–5pm | 77.0% | 0.2% | 461 |
| 5pm–6pm | 69.9% | 1.0% | 932 |
| 6pm–7pm | 64.2% | 0.0% | 137 |
| 7pm–8pm | 72.9% | 1.1% | 470 |
| 8pm–9pm | 74.6% | 1.1% | 184 |
| 10pm–11pm | 82.0% | 0.6% | 705 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on IAD to DEN
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | 88.2% | +4.4 pts | 0.0% | 127 |
| Christmas & New Year (Dec 20 - Jan 3) | 82.5% | -1.3 pts | 1.0% | 302 |
| Summer peak (Jun 15 - Aug 15) | 73.9% | -10.0 pts | 0.7% | 1,260 |
| All other days | 83.8% | — | 0.6% | 5,262 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).