SEA to ONT flight delays & on-time performance
Nonstop flights from Seattle–Tacoma International Airport to Ontario International Airport · 956 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at SEA or ONT right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from Seattle (SEA) to Ontario (ONT) arrived on time 83% of the time in Aug 2025 – Jul 2026, better than the 78% national average.
- 1% were cancelled, and 4% arrived an hour or more late.
- SkyWest Airlines was the most punctual airline here (89% on time); Alaska Airlines was the least (77%).
- Departures scheduled around 7am did best (92% on time); around 1pm did worst (63%).
- Tuesday was the most reliable day to fly (86% on time) and Friday the least (79%).
- The largest source of delay minutes was airline (crew, maintenance, cleaning, fueling) (50%).
Which airline is most on time from SEA to ONT?
Ranked by on-time arrival rate. Regional airlines fly under their partner's brand (e.g. SkyWest for Delta Connection or United Express).
| Airline | On time | Cancelled | Avg delay | 1 hr+ late | Flights |
|---|---|---|---|---|---|
| Delta Air Lines | 93% | 0.0% | 3 min | 0.0% | 29 |
| SkyWest AirlinesRegional airline operating flights for United Express, Delta Connection, American Eagle and Alaska. | 89% | 0.4% | 7 min | 2.5% | 1,047 |
| Frontier Airlines | 84% | 1.8% | 12 min | 6.0% | 169 |
| Alaska Airlines | 77% | 1.5% | 12 min | 4.6% | 1,259 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 7am92%140 flights
- 8am90%473 flights
- 9am88%57 flights
- 10am81%103 flights
- 11am85%208 flights
- 12pm80%166 flights
- 1pm63%94 flights
- 2pm86%316 flights
- 3pm74%151 flights
- 4pm80%40 flights
- 5pm43%37 flights
- 6pm93%44 flights
- 7pm86%288 flights
- 8pm82%197 flights
- 9pm70%188 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday84%0.8% cancelled
- Tuesday86%0.0% cancelled
- Wednesday81%0.6% cancelled
- Thursday81%1.1% cancelled
- Friday79%2.8% cancelled
- Saturday86%0.9% cancelled
- Sunday82%0.8% cancelled
On-time trend by month
Why flights are late
Share of delay minutes by cause, as reported by airlines to the DOT.
- Airline (crew, maintenance, cleaning, fueling)50%
- Late-arriving aircraft27%
- Air traffic control & airport congestion15%
- Extreme weather8%
- Security0%
Why flights are cancelled
Share of cancellations by reason.
- Airline (crew, maintenance, cleaning, fueling)54%
- Air traffic control & airport congestion27%
- Extreme weather19%
- Security0%
SEA to ONT: common questions
- How often are SEA to ONT flights on time?
- 83% of flights arrived less than 15 minutes late in Aug 2025 – Jul 2026, compared with 78% for all US flights.
- How often are flights from Seattle to Ontario cancelled?
- 1.0% of scheduled flights were cancelled (26 of 2,504).
- How long are typical delays?
- Across all flights the average arrival delay was 9 min (early arrivals count as zero). Flights that were late arrived 48 min behind schedule on average, and 3.8% of flights were an hour or more late.
- How long is taxi time at SEA?
- Flights on this route spent 23 min taxiing from the gate to takeoff on average.
Related routes
Return trip: ONT to SEA — 86% on time
More flights from Seattle
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: SEA → ONT, nonstop flights by US airlines that report to the DOT. How we calculate this.