Ontario (ONT) to Seattle (SEA): On-Time Performance
Data through May 2026
The calendar drives reliability on ONT–SEA. February 2026 flights landed on schedule 96% of the time, but January 2025 dropped to 80% — a gap of 15 points. Across the full period the route averages 86% on-time against a national 78%. Morning departures also hold up better than evening ones (90% vs 79%), which matters most in the rough months.
- On-time
- 86%
- arrived <15 min late
- Avg delay
- 10 min
- completed flights
- Cancelled
- 0.9%
- Flights/day
- 7.1
- last 12 months
- Duration
- 2h 50m
- scheduled
- Distance
- 956 mi
Best airline from ONT to SEA
3 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| SkyWest Airlinesmost reliable | 91% | 7 min | 0.2% | 2,251 |
| Frontier Airlines | 83% | 16 min | 1.0% | 418 |
| Alaska Airlines | 82% | 12 min | 1.6% | 2,470 |
Monthly on-time trend
Best time to fly from ONT to SEA
Aim for departures around 7 a.m. (93% on-time); avoid 7 p.m. departures (65%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 85% | 10 min |
| Tuesdaybest | 88% | 7 min |
| Wednesday | 87% | 11 min |
| Thursday | 85% | 11 min |
| Friday | 84% | 10 min |
| Saturday | 87% | 9 min |
| Sunday | 86% | 11 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft36%
- Airline operations42%
- National airspace system16%
- Weather6%
Frequently asked questions
- How often are flights from ONT to SEA delayed?
- 14% of ONT–SEA 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 10 minutes.
- Which airline is most reliable from ONT to SEA?
- SkyWest Airlines has the best on-time record on this route at 91%, based on 2,251 flights. 3 airlines flew ONT–SEA frequently enough to compare in this period.
- What is the best time of day to fly from ONT to SEA?
- Departures around 7 a.m. have the best record (93% on-time), while departures around 7 p.m. have the worst (65%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from ONT to SEA?
- The scheduled ONT–SEA flight time averages 2h 50m over 956 miles. Actual arrival times vary — flights on this route land 15+ minutes late 14% of the time.
- How often are ONT to SEA flights cancelled?
- 0.9% 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 ONT to SEA?
- January 2025 was the roughest month in this dataset, with only 80% of arrivals on time. The best was February 2026 at 96%. If your dates are flexible, that 15-point gap is worth planning around.
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Based on 5,168 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.