Route profile
SEA→DEN
Flight reliability, delays and best times to fly from Seattle to Denver, 1,024 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 61% of comparable major US routes (4,598 compared)
Calculated from 20,291 flights. How this is calculated
SEA → DEN arrives on time 77.9% of the time; the return trip, DEN → SEA, arrives on time 74.7% of the time, a 3.2-point gap between the two directions of the same city pair.
SEA → DEN spends 30.2 minutes on the ground on a 1,024-mile trip: 20.4 minutes from pushback to wheels-up at SEA and 9.7 minutes from touchdown to gate at DEN.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
On-time performance swings unusually widely by time of day here, wider than 92% of 4,023 comparable routes.
88.2% on time for 5–9 AM departures, against 56.6% for 9 PM–5 AM.
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 4,023 in the comparison.
Why SEA → DEN flights are cancelled
July 2023 – July 2026
SEA → DEN cancelled 152 of 20,291 scheduled flights — about 1 in every 133. The reason filed most often was the airline, 69.1% of the cancellations coded on this route — about 1 in every 193 scheduled flights.
Share of cancellations
Of 152 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.
105 cancellations, 69.1% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
32 cancellations, 21.1% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
15 cancellations, 9.9% 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. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
152 coded cancellations were recorded on SEA → DEN; the section appears from 50.
When it goes wrong
July 2023 – July 2026
41 min late
against a median of 5 min early
Percentiles over 20,291 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at DEN after arriving from SEA.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 39% | Likely to miss |
| 45 min | 21% | High risk |
| 60 min | 13% | Some risk |
| 90 min | 6.5% | Some risk |
| 120 min | 3.6% | 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 0.75% of the time and diverts 0.43% of the time, which a late arrival never shows up in.
Chance of missing is the share of 20,052 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 41 minutes late (90th-percentile gate arrival delay), over 20,291 operations.
Any other layover length: connection checker.
Best time to fly
SEA → DEN flights departing 5–9 AM arrived on time 88.2% of the time, against 56.6% for 9 PM–5 AM departures, a gap of 31.6 percentage points.
By day and hour
On-time arrival rate for each weekday and scheduled departure hour, in local time at the departure airport (SEA).
Hour of departure matters more than day of the week: hourly averages sit a typical 9.1 points from the route-wide rate, weekday averages 1.7 points.
| Hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
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On-time rate, % · stronger color, fewer on time
- 50–59
- 60–69
- 70–79
- 80–89
- 90–99
- Fewer than 120 flights, not scored
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · On time is arrival within 15 minutes of schedule. Cells round to whole percentages; the table shows one decimal.
No slot is named best or worst: too few reach 500 flights. Departures after 9 PM (225 flights) are not drawn: no slot in those hours has enough flights to score.
View as tableHide table
| Hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
|---|---|---|---|---|---|---|---|
| 5 AM–6 AM | 96.6% on time293 flights | 95.2% on time230 flights | 98.2% on time228 flights | 95.6% on time297 flights | 91.8% on time296 flights | 92.3% on time288 flights | 94.6% on time297 flights |
| 6 AM–7 AM | 84.7% on time134 flights | 89.3% on time133 flights | 89.9% on time130 flights | 89.1% on time130 flights | 85.7% on time133 flights | 107 flights, too few to score | 88.4% on time131 flights |
| 7 AM–8 AM | 77.4% on time157 flights | 83.2% on time179 flights | 83.8% on time185 flights | 80.8% on time157 flights | 84.6% on time157 flights | 79.5% on time128 flights | 84.6% on time138 flights |
| 8 AM–9 AM | 87.5% on time344 flights | 84.0% on time308 flights | 86.5% on time327 flights | 86.1% on time333 flights | 84.3% on time333 flights | 84.3% on time295 flights | 87.3% on time308 flights |
| 9 AM–10 AM | 111 flights, too few to score | 115 flights, too few to score | 95 flights, too few to score | 115 flights, too few to score | 118 flights, too few to score | 84.2% on time120 flights | 104 flights, too few to score |
| 10 AM–11 AM | 104 flights, too few to score | 77.5% on time122 flights | 77.2% on time127 flights | 112 flights, too few to score | 111 flights, too few to score | 80.6% on time129 flights | 73.1% on time130 flights |
| 11 AM–12 PM | 87.1% on time136 flights | 83.6% on time124 flights | 84.4% on time124 flights | 77.7% on time142 flights | 75.2% on time131 flights | 74.8% on time142 flights | 75.4% on time142 flights |
| 12 PM–1 PM | 78.9% on time259 flights | 81.8% on time237 flights | 83.9% on time228 flights | 75.5% on time246 flights | 81.8% on time256 flights | 81.8% on time235 flights | 79.6% on time231 flights |
| 1 PM–2 PM | 70.5% on time187 flights | 64.1% on time201 flights | 59.6% on time208 flights | 70.4% on time201 flights | 65.7% on time177 flights | 70.3% on time224 flights | 65.9% on time173 flights |
| 2 PM–3 PM | 57.9% on time181 flights | 63.9% on time184 flights | 65.3% on time193 flights | 63.2% on time173 flights | 66.9% on time180 flights | 83 flights, too few to score | 52.8% on time187 flights |
| 3 PM–4 PM | 71.7% on time295 flights | 77.1% on time263 flights | 77.3% on time251 flights | 69.7% on time290 flights | 71.1% on time304 flights | 74.8% on time242 flights | 72.0% on time288 flights |
| 4 PM–5 PM | 107 flights, too few to score | 85 flights, too few to score | 87 flights, too few to score | 110 flights, too few to score | 112 flights, too few to score | 94 flights, too few to score | 104 flights, too few to score |
| 5 PM–6 PM | 98 flights, too few to score | 75 flights, too few to score | 70 flights, too few to score | 86 flights, too few to score | 87 flights, too few to score | 76 flights, too few to score | 111 flights, too few to score |
| 6 PM–7 PM | 103 flights, too few to score | 100 flights, too few to score | 83.3% on time128 flights | 104 flights, too few to score | 110 flights, too few to score | 106 flights, too few to score | 97 flights, too few to score |
| 7 PM–8 PM | 72.2% on time274 flights | 77.0% on time210 flights | 81.5% on time265 flights | 73.4% on time300 flights | 74.4% on time273 flights | 84.2% on time215 flights | 70.6% on time285 flights |
| 8 PM–9 PM | 77.6% on time205 flights | 76.3% on time156 flights | 73.9% on time163 flights | 66.9% on time180 flights | 73.6% on time212 flights | 81.0% on time145 flights | 67.1% on time226 flights |
By departure window
By departure hour
- 12 AM to 4 AM: too few flights to score
- 5 AM: 94.8% on time from 1,929 flights
- 6 AM: 87.6% on time from 898 flights
- 7 AM: 82.1% on time from 1,101 flights
- 8 AM: 85.7% on time from 2,248 flights
- 9 AM: 88.0% on time from 778 flights
- 10 AM: 76.4% on time from 835 flights
- 11 AM: 79.6% on time from 941 flights
- 12 PM: 80.4% on time from 1,692 flights
- 1 PM: 66.6% on time from 1,371 flights
- 2 PM: 62.2% on time from 1,181 flights
- 3 PM: 73.2% on time from 1,933 flights
- 4 PM: 67.0% on time from 699 flights
- 5 PM: 63.6% on time from 603 flights
- 6 PM: 75.6% on time from 748 flights
- 7 PM: 75.8% on time from 1,822 flights
- 8 PM: 73.3% on time from 1,287 flights
- 9 PM: 60.1% on time from 171 flights
- 10 PM to 11 PM: too few flights to score
Why SEA → 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 SEA → DEN. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on SEA → DEN, at 36.2%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 88.2% of the time and 9 PM–5 AM departures 56.6%.
How this route holds up in bad weather
July 2023 – July 2026
The harder-hit end is DEN, where the flight lands. Its figure counts departures from DEN, so it says more about how that airport copes than about this route. Bad weather cancels 4.0 times the normal rate at DEN against 1.9 times at SEA. Cancelled in bad weather against normal hours: SEA 1.5% against 0.8%, 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 | SEA | DEN |
|---|---|---|
| Cancelled in bad weather | 1.5% | 2.8% |
| Cancelled in normal hours | 0.8% | 0.7% |
| Arrived on time, bad weather | 75.4% | 51.5% |
| Arrived on time, normal hours | 79.3% | 78.8% |
| Departures in bad weather | 43,416 | 92,610 |
Of the carriers on this route, Southwest Airlines (0.4% cancelled against 1.5% for the other carriers at SEA) cancelled the fewest departures from SEA in bad weather and Alaska Airlines (1.8% cancelled against 1.2% for the other carriers at SEA) the most. One more carrier flies this route but has too few bad-weather departures from SEA to compare.
This route’s airlines in bad weather at SEA
All departures from SEA| Airline | Bad-weather departures | Cancelled | Other carriers |
|---|---|---|---|
| Southwest Airlines | 2,229 | 0.4%below the others | 1.5% |
| United Airlines | 2,531 | 0.8%below the others | 1.5% |
| Delta Air Lines | 9,020 | 1.1%below the others | 1.6% |
| SkyWest Airlines | 6,711 | 1.9%above the others | 1.5% |
| Alaska Airlines | 20,261 | 1.8%above the others | 1.2% |
These are airport figures, not route figures: every scheduled departure from SEA and DEN, to any destination, in hours the weather report called bad. The airline rows count each carrier’s departures from SEA on every route.
Weather source and limits. In full: SEA (airlines), 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 | 6,060 | 86.6% | 0.94% | -11 min | 5.1% |
| Alaska Airlines | 4,902 | 75.1% | 0.71% | -2 min | 6.3% |
| Southwest Airlines | 4,524 | 72.6% | 0.40% | 1 min | 7.2% |
| Delta Air Lines | 2,874 | 75.3% | 0.66% | -5 min | 8.0% |
| Frontier Airlines | 1,435 | 71.7% | 1.46% | -1 min | 10.3% |
| SkyWest Airlines | 496 | 82.8% | 0.40% | -8 min | 5.7% |
United Airlines flew 29.9% of the 20,291 flights listed. Frontier Airlines cancelled 1.46% of its flights here against 0.40% for Southwest Airlines.
United Airlines arrived on time 14.9 percentage points more often than Frontier Airlines on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
UA757 (3:48 PM) arrived on time 84.3% of the time, 8.8 points more often than AS642 (8:20 PM) at 75.5%.
Weekly and seasonal patterns
By day of week
Saturday is historically the most reliable day and Sunday the least, a gap of 5.1 percentage points.
By month
- Jan: 84.9%
- Feb: 82.8%
- Mar: 80.7%
- Apr: 80.8%
- May: 76.2%
- Jun: 70.0%
- Jul: 69.3%
- Aug: 70.1%
- Sep: 79.1%
- Oct: 83.9%
- Nov: 86.9%
- Dec: 83.4%
July is historically the weakest month and November the strongest, a spread of 17.6 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 71.1% from 657 flights
- August 2023: 75.0% from 654 flights
- September 2023: 80.3% from 602 flights
- October 2023: 83.1% from 581 flights
- November 2023: 85.7% from 520 flights
- December 2023: 83.1% from 533 flights
- January 2024: 80.1% from 482 flights
- February 2024: 83.7% from 449 flights
- March 2024: 78.8% from 494 flights
- April 2024: 80.4% from 504 flights
- May 2024: 78.6% from 600 flights
- June 2024: 72.4% from 683 flights
- July 2024: 76.2% from 718 flights
- August 2024: 69.3% from 671 flights
- September 2024: 80.9% from 606 flights
- October 2024: 85.5% from 568 flights
- November 2024: 88.8% from 485 flights
- December 2024: 86.8% from 469 flights
- January 2025: 87.4% from 447 flights
- February 2025: 79.5% from 411 flights
- March 2025: 84.1% from 473 flights
- April 2025: 74.6% from 482 flights
- May 2025: 67.4% from 564 flights
- June 2025: 65.2% from 643 flights
- July 2025: 61.3% from 670 flights
- August 2025: 65.9% from 644 flights
- September 2025: 75.9% from 574 flights
- October 2025: 83.2% from 557 flights
- November 2025: 86.1% from 466 flights
- December 2025: 80.5% from 468 flights
- January 2026: 87.4% from 429 flights
- February 2026: 85.1% from 403 flights
- March 2026: 79.2% from 455 flights
- April 2026: 87.6% from 470 flights
- May 2026: 82.6% from 546 flights
- June 2026: 72.2% from 635 flights
- July 2026: 68.2% from 678 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 78.5% against 76.5% in the 12 months before — improving by 2.0 percentage points.
Data and methodology
Calculated by FlyerIntel from 20,291 SEA → 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