ONT to SEA flight delays
Ontario, CA (ONT) Seattle, WA (SEA) · 956 miles
240 flights · March 2025 – August 2026 · US Bureau of Transportation Statistics
84.39%
Arrived on time
Within 15 minutes of schedule
1.25%
Cancelled
Share of scheduled flights
41 min
When late, late by
Average across delayed arrivals
7 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 ONT overall run 10.7 points less punctual than this particular one — so whatever congestion ONT 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.
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.
Flights from Ontario to Seattle keep to schedule more reliably than most. On a route this punctual the day you fly matters more than the airline you pick.
Which airline should you fly on this route?
Over March 2025 – August 2026, Alaska Airlines arrived on time most often on ONT to SEA.
Every airline on ONT to SEA
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 | 76.92% | 2.5% | 31 min | C |
| SkyWest Airlines | 92 | 95.65% | 0% | 54 min | — |
| Frontier Airlines | 28 | 78.57% | 0% | 75 min | — |
The return leg
SEA to ONT Seattle back to Ontario 85.59% on time BOther routes from Ontario
Common questions
Are flights from Ontario to Seattle usually delayed?
84.39% of flights on the ONT to SEA route arrived within 15 minutes of schedule, so roughly 2 in every ten arrived late. That is better than the average route in this record.
Which airlines fly from Ontario to Seattle?
Only Alaska Airlines appears in the published record on this route, with 120 flights and 76.92% arriving on time.
How often are ONT to SEA flights cancelled?
1.25% of scheduled flights did not operate — about 13 in every thousand. That is in the normal range.
When ONT to SEA flights are late, how late are they?
About 41 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 ONT to SEA 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 →