Flight history · Aug 2025 – Jul 2026 · US DOT on-time records
WN 3856 · Denver (DEN) → Seattle (SEA)
Sold by Southwest. Still flying: 55 of the last 56 days (Daily).
Arrives on time28%within 15 minutes, of 57 flights
Cancelled0.0%of scheduled flights
An hour or more late30%of flights that operated
When late, on average63 minlate, among flights 15+ min late
Schedule
Typical times in the Jun 6 – Jul 31, 2026 schedule, local at each airport (Seattle is 1 h behind Denver).
- Leaves DEN
- 21:10
- Arrives SEA
- 23:10
- Flight time
- 2h 55m
- Days flown, last 8 weeks
- 55 of 56
Each square is a day, Sat Jun 6 to Fri Jul 31, two weeks per row (each column is the same weekday); filled = flew.
How late it arrives
Share of flights that operated arriving more than this late.
Horizontal: minutes late at arrival (0 to 3 hours). Vertical: share of flights later than that.
Its hour at DEN
All flights leaving Denver (DEN) at 9–10 pm, wherever they’re going: 67% left within 15 minutes and 0.7% were cancelled (10,147 flights in the year). Other Southwest flights on this route →
Upcoming forecasts
Our odds that this flight is late or cancelled on the days we publish.