Best Time to Fly ONT to SEA: On-Time Stats by Hour & Airline
Ontario International → Seattle/Tacoma International
Data through July 2026 · Last updated October 18, 2026
Over the last 12 months, 86.3% of Ontario (ONT) to Seattle (SEA) flights arrived on time (2,505 scheduled flights). That is 8.7 points above the national average of 77.6%.
Among 3 airlines, SkyWest Airlines led with 91.8% on time and Frontier Airlines was last with 82.1%.
Over 24 months, Tuesday was the most reliable day (88% on time) and July the worst month (81%).
The cancellation rate was 1.1% (US average 1.8%).
ONT to SEA on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| SkyWest Airlines | 91.8% | 90 min | 0.3% | 1,048 |
| Alaska Airlines | 82.2% | 52 min | 1.8% | 1,259 |
| Frontier Airlines | 82.1% | 92 min | 0.6% | 169 |
| Delta Air Lines | Limited data | 29 | ||
80%+ good 70–79.9% fair <70% poor
Best time of day to fly ONT to SEA
On-time arrival % by scheduled departure hour (local time), 5,118 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 5am–6am | 93.8% | 0.0% | 99 |
| 6am–7am | 92.0% | 0.5% | 1,127 |
| 7am–8am | 92.8% | 0.0% | 237 |
| 8am–9am | 82.2% | 0.0% | 45 |
| 9am–10am | Limited data | 16 | |
| 10am–11am | 87.1% | 0.6% | 320 |
| 11am–12pm | 90.4% | 1.2% | 822 |
| 12pm–1pm | 84.0% | 6.6% | 228 |
| 1pm–2pm | 76.8% | 0.0% | 82 |
| 2pm–3pm | 81.2% | 0.7% | 294 |
| 3pm–4pm | 89.3% | 0.0% | 178 |
| 4pm–5pm | 81.2% | 1.9% | 565 |
| 5pm–6pm | 89.2% | 0.4% | 492 |
| 6pm–7pm | 72.6% | 0.5% | 220 |
| 7pm–8pm | 65.0% | 0.8% | 259 |
| 8pm–9pm | 76.8% | 0.0% | 99 |
| 9pm–10pm | 57.1% | 0.0% | 35 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on ONT to SEA
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | 83.7% | -3.5 pts | 0.0% | 100 |
| Christmas & New Year (Dec 20 - Jan 3) | 82.6% | -4.6 pts | 1.1% | 181 |
| Summer peak (Jun 15 - Aug 15) | 82.3% | -4.9 pts | 1.6% | 1,099 |
| All other days | 87.2% | — | 0.9% | 3,738 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).