Seattle (SEA) to Ontario (ONT): On-Time Performance
Data through July 2026
The calendar drives reliability on SEA–ONT. September 2025 flights landed on schedule 91% of the time, but July 2026 dropped to 68% — a gap of 23 points. Across the full period the route averages 82% on-time against a national 78%. Morning departures also hold up better than evening ones (89% vs 79%), which matters most in the rough months.
- On-time
- 82%
- arrived <15 min late
- Avg delay
- 10 min
- completed flights
- Cancelled
- 1.1%
- Flights/day
- 6.9
- last 12 months
- Duration
- 2h 43m
- scheduled
- Distance
- 956 mi
Best airline from SEA to ONT
3 airlines flew this route regularly between 2024-07 and 2026-07.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| SkyWest Airlinesmost reliable | 90% | 6 min | 0.2% | 2,307 |
| Frontier Airlines | 77% | 17 min | 2.5% | 448 |
| Alaska Airlines | 77% | 12 min | 1.6% | 2,612 |
Monthly on-time trend
Best time to fly from SEA to ONT
Aim for departures around 6 a.m. (92% on-time); avoid 9 p.m. departures (67%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 83% | 10 min |
| Tuesdaybest | 86% | 7 min |
| Wednesday | 84% | 10 min |
| Thursday | 79% | 12 min |
| Friday | 81% | 10 min |
| Saturday | 85% | 8 min |
| Sunday | 79% | 10 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft33%
- Airline operations46%
- National airspace system14%
- Weather6%
Frequently asked questions
- How often are flights from SEA to ONT delayed?
- 18% of SEA–ONT flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-07 and 2026-07. The average arrival delay across completed flights was 10 minutes.
- Which airline is most reliable from SEA to ONT?
- SkyWest Airlines has the best on-time record on this route at 90%, based on 2,307 flights. 3 airlines flew SEA–ONT frequently enough to compare in this period.
- What is the best time of day to fly from SEA to ONT?
- Departures around 6 a.m. have the best record (92% on-time), while departures around 9 p.m. have the worst (67%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from SEA to ONT?
- The scheduled SEA–ONT flight time averages 2h 43m over 956 miles. Actual arrival times vary — flights on this route land 15+ minutes late 18% of the time.
- How often are SEA to ONT flights cancelled?
- 1.1% of scheduled flights on this route were cancelled between 2024-07 and 2026-07, at or below the national rate of 1.6%.
- What is the worst month to fly from SEA to ONT?
- July 2026 was the roughest month in this dataset, with only 68% of arrivals on time. The best was September 2025 at 91%. If your dates are flexible, that 23-point gap is worth planning around.
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Based on 5,396 flights, 2024-07–2026-07. Source: US DOT Bureau of Transportation Statistics. Updated 2026-09-28.