Route profile
SLC→SEA
Flight reliability, delays and best times to fly from Salt Lake City to Seattle, 689 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 84% of comparable major US routes (4,598 compared)
Calculated from 12,345 flights. How this is calculated
SLC → SEA arrives on time 80.7% of the time; the return trip, SEA → SLC, arrives on time 83.4% of the time, a 2.7-point gap between the two directions of the same city pair.
SLC → SEA spends 32.4 minutes on the ground on a 689-mile trip: 20.5 minutes from pushback to wheels-up at SLC and 11.9 minutes from touchdown to gate at SEA.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
This route has stayed remarkably steady year over year, a smaller swing than 93% of 5,368 comparable routes.
80.1% on time over the most recent 12 months (2025-08 to 2026-07), against 80.5% in the 12 months before (2024-08 to 2025-07), virtually unchanged.
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 5,368 in the comparison.
Why SLC → SEA flights are cancelled
July 2023 – July 2026
SLC → SEA cancelled 83 of 12,345 scheduled flights — about 1 in every 149. The reason filed most often was the airline, 74.7% of the cancellations coded on this route — about 1 in every 199 scheduled flights.
Share of cancellations
Of 83 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.
62 cancellations, 74.7% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
14 cancellations, 16.9% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
7 cancellations, 8.4% 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.
83 coded cancellations were recorded on SLC → SEA; the section appears from 50.
When it goes wrong
July 2023 – July 2026
30 min late
against a median of 6 min early
Percentiles over 12,345 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SEA after arriving from SLC.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 36% | Likely to miss |
| 45 min | 18% | High risk |
| 60 min | 9.9% | Some risk |
| 90 min | 4.1% | Low risk |
| 120 min | 2.1% | 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 0.67% of the time and diverts 0.12% of the time, which a late arrival never shows up in.
Chance of missing is the share of 12,247 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 30 minutes late (90th-percentile gate arrival delay), over 12,345 operations.
Any other layover length: connection checker.
Best time to fly
SLC → SEA flights departing 5–9 AM arrived on time 91.2% of the time, against 63.8% for 6–9 PM departures, a gap of 27.4 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 92.2% on time from 658 flights
- 7 AM: 90.9% on time from 1,145 flights
- 8 AM: 90.8% on time from 852 flights
- 9 AM: 59.4% on time from 617 flights
- 10 AM: 85.8% on time from 150 flights
- 11 AM: 87.6% on time from 1,823 flights
- 12 PM: 81.6% on time from 359 flights
- 1 PM: 83.5% on time from 698 flights
- 2 PM: 85.9% on time from 131 flights
- 3 PM: 75.6% on time from 1,564 flights
- 4 PM: 76.7% on time from 319 flights
- 5 PM: 82.7% on time from 1,291 flights
- 6 PM: 77.2% on time from 200 flights
- 7 PM: 64.7% on time from 490 flights
- 8 PM: 59.5% on time from 704 flights
- 9 PM: 70.4% on time from 534 flights
- 10 PM: 87.0% on time from 636 flights
- 11 PM: 85.7% on time from 155 flights
Why SLC → SEA runs late
July 2023 – July 2026
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
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 SLC → SEA. Only delays of 15 minutes or more are attributed.
How this route holds up in bad weather
July 2023 – July 2026
The harder-hit end is SEA, where the flight lands. Its figure counts departures from SEA, so it says more about how that airport copes than about this route. Bad weather cancels 1.9 times the normal rate at SEA against barely any change at SLC. Cancelled in bad weather against normal hours: SLC 0.6% against 0.6%, SEA 1.5% against 0.8%. Flights that did leave SLC in bad weather arrived on time 71.0% of the time, against 84.8% in normal hours.
Bad weather and normal hours at the airports
Scheduled departures, July 2023 – July 2026| Departures from | SLC | SEA |
|---|---|---|
| Cancelled in bad weather | 0.6% | 1.5% |
| Cancelled in normal hours | 0.6% | 0.8% |
| Arrived on time, bad weather | 71.0% | 75.4% |
| Arrived on time, normal hours | 84.8% | 79.3% |
| Departures in bad weather | 20,014 | 43,416 |
SkyWest Airlines (0.4% cancelled against 0.7% for the other carriers at SLC) cancelled fewer departures from SLC in bad weather than the other carriers there did in the same months. None of the route’s other carriers was clearly worse. One more carrier flies this route but has too few bad-weather departures from SLC to compare.
This route’s airlines in bad weather at SLC
All departures from SLC| Airline | Bad-weather departures | Cancelled | Other carriers |
|---|---|---|---|
| SkyWest Airlines | 5,888 | 0.4%below the others | 0.7% |
| Delta Air Lines | 9,247 | 0.5%about level | 0.7% |
These are airport figures, not route figures: every scheduled departure from SLC and SEA, to any destination, in hours the weather report called bad. The airline rows count each carrier’s departures from SLC on every route.
Weather source and limits. In full: SLC (airlines), SEA, 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 |
|---|---|---|---|---|---|
| Delta Air Lines | 6,825 | 84.7% | 0.38% | -9 min | 3.8% |
| Alaska Airlines | 3,887 | 75.1% | 1.36% | -3 min | 4.6% |
| SkyWest Airlines | 1,441 | 78.0% | 0.00% | -3 min | 4.3% |
Delta Air Lines flew 56.2% of the 12,153 flights listed. Alaska Airlines cancelled 1.36% of its flights here against 0.00% for SkyWest Airlines.
Delta Air Lines arrived on time 9.6 percentage points more often than Alaska Airlines on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
DL2874 (8:00 AM) arrived on time 92.2% of the time, 14.0 points more often than DL2817 (3:30 PM) at 78.2%.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 6.5 percentage points.
By month
- Jan: 80.2%
- Feb: 86.5%
- Mar: 84.4%
- Apr: 86.3%
- May: 79.2%
- Jun: 72.3%
- Jul: 74.1%
- Aug: 74.9%
- Sep: 84.0%
- Oct: 85.6%
- Nov: 86.3%
- Dec: 82.6%
June is historically the weakest month and February the strongest, a spread of 14.2 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 77.6% from 353 flights
- August 2023: 81.9% from 351 flights
- September 2023: 85.5% from 352 flights
- October 2023: 86.6% from 290 flights
- November 2023: 85.5% from 276 flights
- December 2023: 90.1% from 273 flights
- January 2024: 73.1% from 286 flights
- February 2024: 88.8% from 269 flights
- March 2024: 86.1% from 275 flights
- April 2024: 86.9% from 306 flights
- May 2024: 81.0% from 364 flights
- June 2024: 73.3% from 382 flights
- July 2024: 70.8% from 397 flights
- August 2024: 71.6% from 383 flights
- September 2024: 84.7% from 367 flights
- October 2024: 91.3% from 335 flights
- November 2024: 89.8% from 317 flights
- December 2024: 87.8% from 304 flights
- January 2025: 83.0% from 319 flights
- February 2025: 83.5% from 281 flights
- March 2025: 82.8% from 306 flights
- April 2025: 82.7% from 307 flights
- May 2025: 74.0% from 360 flights
- June 2025: 66.8% from 373 flights
- July 2025: 74.1% from 394 flights
- August 2025: 72.0% from 409 flights
- September 2025: 82.1% from 398 flights
- October 2025: 79.6% from 367 flights
- November 2025: 83.4% from 299 flights
- December 2025: 70.7% from 303 flights
- January 2026: 83.9% from 299 flights
- February 2026: 87.3% from 293 flights
- March 2026: 84.3% from 335 flights
- April 2026: 89.2% from 315 flights
- May 2026: 82.8% from 338 flights
- June 2026: 76.8% from 358 flights
- July 2026: 74.1% from 411 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 80.1% against 80.5% in the 12 months before — broadly unchanged.
Data and methodology
Calculated by FlyerIntel from 12,345 SLC → SEA 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