Ontario to Seattle

What the Data Says About ONT to SEA

The Ontario to Seattle corridor (ONT → SEA) covers roughly 956 miles and is served by 17 carriers, based on Bureau of Transportation Statistics reporting. Across 12,860 flights in the dataset, this route posts a 87.1% on-time rate with an average delay of 69.4 minutes when flights run late. Over the most recent 24 months of BTS data, 5,131 flights were recorded on this pairing — 60 cancelled (1.2%) and 8 diverted (0.2%). Those baseline metrics tell you what to expect before you book.

Having 17 carriers on the route matters: more carriers generally means more daily schedule options, competitive pricing, and redundancy when flights are cancelled. With 12,860 total flights analyzed, the 87.1% on-time figure is statistically meaningful rather than a small-sample fluke. The 69.4-minute average delay applies only to flights that actually ran late, so it is not the average wait across all departures — the majority of flights on this route depart on time under the BTS definition of a delay (15+ minutes past schedule).

Looking at recent months, Oct 2024 posted the best performance on this corridor at 94% on-time, while Feb 2025 came in at 81% on-time — a 13-point gap between best and worst recent month. For travelers evaluating the ONT to SEA route, the combination of a 87.1% on-time rate, 69.4-minute average delay, 1.2% recent cancellation rate, and 17 available carriers is the concrete summary of what BTS data shows about reliability on this pairing.