ONT to SEA flight delays & on-time performance
Nonstop flights from Ontario International Airport to Seattle–Tacoma International Airport · 956 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at ONT or SEA right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from Ontario (ONT) to Seattle (SEA) arrived on time 86% of the time in Aug 2025 – Jul 2026, better than the 78% national average.
- 1.1% were cancelled, and 4% arrived an hour or more late.
- SkyWest Airlines was the most punctual airline here (92% on time); Frontier Airlines was the least (82%).
- Departures scheduled around 7am did best (94% on time); around 7pm did worst (69%).
- Tuesday was the most reliable day to fly (89% on time) and Thursday the least (83%).
- The largest source of delay minutes was airline (crew, maintenance, cleaning, fueling) (43%).
Which airline is most on time from ONT to SEA?
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 | 3.4% | 29 |
| SkyWest AirlinesRegional airline operating flights for United Express, Delta Connection, American Eagle and Alaska. | 92% | 0.3% | 8 min | 2.8% | 1,048 |
| Alaska Airlines | 82% | 1.8% | 10 min | 4.0% | 1,259 |
| Frontier Airlines | 82% | 0.6% | 17 min | 5.4% | 169 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 6am94%593 flights
- 7am94%121 flights
- 8am86%28 flights
- 10am89%112 flights
- 11am93%369 flights
- 12pm83%167 flights
- 1pm79%53 flights
- 2pm77%118 flights
- 3pm89%133 flights
- 4pm80%242 flights
- 5pm84%290 flights
- 6pm79%99 flights
- 7pm69%135 flights
- 9pm57%30 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday86%0.5% cancelled
- Tuesday89%0.0% cancelled
- Wednesday87%0.6% cancelled
- Thursday83%0.8% cancelled
- Friday85%2.8% cancelled
- Saturday89%1.6% cancelled
- Sunday87%1.0% 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)43%
- Late-arriving aircraft37%
- Air traffic control & airport congestion15%
- Extreme weather5%
- Security0%
Why flights are cancelled
Share of cancellations by reason.
- Airline (crew, maintenance, cleaning, fueling)63%
- Air traffic control & airport congestion26%
- Extreme weather11%
- Security0%
ONT to SEA: common questions
- How often are ONT to SEA flights on time?
- 86% 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 Ontario to Seattle cancelled?
- 1.1% of scheduled flights were cancelled (27 of 2,505).
- How long are typical delays?
- Across all flights the average arrival delay was 10 min (early arrivals count as zero). Flights that were late arrived 65 min behind schedule on average, and 3.6% of flights were an hour or more late.
- How long is taxi time at ONT?
- Flights on this route spent 16 min taxiing from the gate to takeoff on average.
Related routes
Return trip: SEA to ONT — 83% on time
More flights from Ontario
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: ONT → SEA, nonstop flights by US airlines that report to the DOT. How we calculate this.