Seattle (SEA) to Denver (DEN): On-Time Performance
Data through May 2026
The calendar drives reliability on SEA–DEN. November 2024 flights landed on schedule 89% of the time, but July 2025 dropped to 60% — a gap of 29 points. Across the full period the route averages 78% on-time against a national 78%. Morning departures also hold up better than evening ones (86% vs 72%), which matters most in the rough months.
- On-time
- 78%
- arrived <15 min late
- Avg delay
- 14 min
- completed flights
- Cancelled
- 0.6%
- Flights/day
- 17
- last 12 months
- Duration
- 2h 45m
- scheduled
- Distance
- 1,024 mi
Best airline from SEA to DEN
6 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| United Airlinesmost reliable | 86% | 11 min | 0.7% | 3,826 |
| SkyWest Airlines | 83% | 11 min | 0.4% | 489 |
| Delta Air Lines | 74% | 18 min | 0.8% | 1,690 |
| Alaska Airlines | 73% | 15 min | 0.5% | 3,187 |
| Southwest Airlines | 73% | 15 min | 0.3% | 2,780 |
| Frontier Airlines | 73% | 21 min | 1.5% | 930 |
Monthly on-time trend
Best time to fly from SEA to DEN
Aim for departures around 5 a.m. (96% on-time); avoid 4 p.m. departures (58%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 78% | 14 min |
| Tuesday | 78% | 13 min |
| Wednesday | 79% | 12 min |
| Thursday | 77% | 15 min |
| Friday | 76% | 16 min |
| Saturdaybest | 80% | 14 min |
| Sunday | 75% | 17 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft34%
- Airline operations32%
- National airspace system31%
- Weather4%
Frequently asked questions
- How often are flights from SEA to DEN delayed?
- 23% of SEA–DEN flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-06 and 2026-05. The average arrival delay across completed flights was 14 minutes.
- Which airline is most reliable from SEA to DEN?
- United Airlines has the best on-time record on this route at 86%, based on 3,826 flights. 6 airlines flew SEA–DEN frequently enough to compare in this period.
- What is the best time of day to fly from SEA to DEN?
- Departures around 5 a.m. have the best record (96% on-time), while departures around 4 p.m. have the worst (58%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from SEA to DEN?
- The scheduled SEA–DEN flight time averages 2h 45m over 1,024 miles. Actual arrival times vary — flights on this route land 15+ minutes late 23% of the time.
- How often are SEA to DEN flights cancelled?
- 0.6% of scheduled flights on this route were cancelled between 2024-06 and 2026-05, at or below the national rate of 1.6%.
- What is the worst month to fly from SEA to DEN?
- July 2025 was the roughest month in this dataset, with only 60% of arrivals on time. The best was November 2024 at 89%. If your dates are flexible, that 29-point gap is worth planning around.
Explore related pages
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Based on 12,902 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.