SEA to ONT flight delays
Seattle, WA (SEA) Ontario, CA (ONT) · 956 miles
240 flights · March 2025 – August 2026 · US Bureau of Transportation Statistics
85.59%
Arrived on time
Within 15 minutes of schedule
1.67%
Cancelled
Share of scheduled flights
46 min
When late, late by
Average across delayed arrivals
8 min
Delay per flight
Averaged over every flight flown
What the record says about this route
This route does better than its own airport. Departures from SEA overall run 11.2 points less punctual than this particular one — so whatever congestion SEA has, this route is largely escaping it.
Only Alaska Airlines flies this route in the published record, so there is no choice to weigh — the route's figures and the airline's are the same figures.
Flights from Seattle to Ontario keep to schedule more reliably than most. On a route this punctual the day you fly matters more than the airline you pick.
This is a thin route — 240 flights across the whole period. On a route this infrequent a cancellation is far more costly than the rate suggests, because the next departure may not be the same day.
Which airline should you fly on this route?
Over March 2025 – August 2026, Alaska Airlines arrived on time most often on SEA to ONT.
Every airline on SEA to ONT
Ranked by how many flights each one operated. A carrier with fewer than 100 flights in the period is listed but not graded.
| Airline | Flights | On time | Cancelled | Avg delay | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 120 | 81.2% | 2.5% | 38 min | C |
| SkyWest Airlines | 92 | 90.22% | 0% | 23 min | — |
| Frontier Airlines | 28 | 88.89% | 3.57% | 175 min | — |
The return leg
ONT to SEA Ontario back to Seattle 84.39% on time BOther routes from Seattle
Common questions
Are flights from Seattle to Ontario usually delayed?
85.59% of flights on the SEA to ONT route arrived within 15 minutes of schedule, so roughly 1 in every ten arrived late. That is better than the average route in this record.
Which airlines fly from Seattle to Ontario?
Only Alaska Airlines appears in the published record on this route, with 120 flights and 81.2% arriving on time.
How often are SEA to ONT flights cancelled?
1.67% of scheduled flights did not operate — about 17 in every thousand. That is in the normal range.
When SEA to ONT flights are late, how late are they?
About 46 minutes on average across the flights that arrived more than 15 minutes behind schedule.
What these figures do and do not tell you
Everything on this page is counted from the flights that actually operated on SEA to ONT during March 2025 – August 2026, as reported by the airlines to the US Bureau of Transportation Statistics. "On time" is the federal definition: arriving at the gate within 15 minutes of the scheduled time.
A route's record is a description of the past, not a forecast. Weather, air traffic control and the aircraft's earlier flights that day drive most delays, and none of them are predictable from a historical rate. What the record does tell you is whether this route runs late more often than others, and which carrier on it has the better history — which is the part you can actually act on when you book.
Cancellations are counted separately from delays because they are a different problem for a traveller: a late flight still gets you there. How the grade is calculated →