76% of SEA → ONT flights arrived on time in June-August 2026 (730 flights). The most reliable was AS 1364, on time 92% of the time on this route. Morning flights did best (86%), afternoon flights worst (64%). Seattle (SEA): no delay reported. ONT (ONT): no delay reported.
Best time of day to fly SEA → ONT
| Morning (before noon) | |
| Afternoon (noon-5 PM) | |
| Evening (after 5 PM) |
Flights SEA → ONT, most reliable first
| Flight | Departs | On time on this route | Cancelled |
|---|---|---|---|
| AS 1364 Alaska Airlines | 8:33 AM | 3.3% | |
| OO 4070 SkyWest | 8:25 AM | 0% | |
| OO 3884 SkyWest | 7:50 PM | 0% | |
| F9 2276 Frontier | 11:54 AM | 3.3% | |
| OO 4031 SkyWest | 2:30 PM | 0% | |
| AS 565 Alaska Airlines | 10:25 AM | 2.2% | |
| AS 489 Alaska Airlines | 8:33 PM | 0% | |
| AS 592 Alaska Airlines | 5:51 PM | 0% | |
| AS 571 Alaska Airlines | 1:50 PM | 1.4% |
SEA conditions · ONT → SEA · Cancellations
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From BTS on-time data, June-August 2026; flights with 20+ trips on this route. On-time rates cover each flight number's whole day, which can include other legs. Departure times are local.