SEA to DEN flight delays
Seattle, WA (SEA) Denver, CO (DEN) · 1,024 miles
635 flights · March 2025 – August 2026 · US Bureau of Transportation Statistics
72.2%
Arrived on time
Within 15 minutes of schedule
1.1%
Cancelled
Share of scheduled flights
57 min
When late, late by
Average across delayed arrivals
17 min
Delay per flight
Averaged over every flight flown
What the record says about this route
Which airline you fly changes the odds here. United Airlines arrived on time 32.8 points more often than Southwest Airlines over the same period on the same route — same airports, same weather, same air traffic control. A gap that survives all of that is about how the two airlines are run.
Flights from Seattle to Denver run late more often than the average route, though not severely.
Which airline should you fly on this route?
Over March 2025 – August 2026, United Airlines arrived on time most often on SEA to DEN. Southwest Airlines was late most often.
Every airline on SEA to DEN
Ranked by how many flights each one operated. A carrier with fewer than 100 flights in the period is listed but not graded.
| Airline | Flights | On time | Cancelled | Avg delay | Grade |
|---|---|---|---|---|---|
| United Airlines | 197 | 85.71% | 0% | 61 min | A |
| Alaska Airlines | 150 | 73.47% | 2% | 45 min | C |
| Southwest Airlines | 141 | 52.86% | 0% | 63 min | F |
| Delta Air Lines | 90 | 68.18% | 2.22% | 56 min | — |
| Frontier Airlines | 57 | 76.36% | 3.51% | 53 min | — |
The return leg
DEN to SEA Denver back to Seattle 69.65% on time DOther routes from Seattle
Common questions
Are flights from Seattle to Denver usually delayed?
72.2% of flights on the SEA to DEN route arrived within 15 minutes of schedule, so roughly 3 in every ten arrived late. That is worse than the average route in this record.
Which airline is most on time from Seattle to Denver?
United Airlines, at 85.71% on time across 197 flights. The least punctual on the route was Southwest Airlines at 52.86%.
How often are SEA to DEN flights cancelled?
1.1% of scheduled flights did not operate — about 11 in every thousand. That is in the normal range.
When SEA to DEN flights are late, how late are they?
About 57 minutes on average across the flights that arrived more than 15 minutes behind schedule.
What these figures do and do not tell you
Everything on this page is counted from the flights that actually operated on SEA to DEN during March 2025 – August 2026, as reported by the airlines to the US Bureau of Transportation Statistics. "On time" is the federal definition: arriving at the gate within 15 minutes of the scheduled time.
A route's record is a description of the past, not a forecast. Weather, air traffic control and the aircraft's earlier flights that day drive most delays, and none of them are predictable from a historical rate. What the record does tell you is whether this route runs late more often than others, and which carrier on it has the better history — which is the part you can actually act on when you book.
Cancellations are counted separately from delays because they are a different problem for a traveller: a late flight still gets you there. How the grade is calculated →