Ontario (ONT) to San Francisco (SFO): On-Time Performance
Data through May 2026
When you fly ONT to SFO matters as much as anything else about the booking: the route swung from 91% on-time in March 2026 to just 43% in May 2026. Across the full period the route averages 75% on-time against a national 78%. Morning departures also hold up better than evening ones (79% vs 64%), which matters most in the rough months.
- On-time
- 75%
- arrived <15 min late
- Avg delay
- 18 min
- completed flights
- Cancelled
- 1.2%
- Flights/day
- 3.5
- last 12 months
- Duration
- 1h 30m
- scheduled
- Distance
- 363 mi
Best airline from ONT to SFO
3 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| SkyWest Airlinesmost reliable | 78% | 18 min | 1.7% | 889 |
| United Airlines | 78% | 16 min | 0.6% | 1,509 |
| Frontier Airlines | 59% | 27 min | 2.3% | 471 |
Monthly on-time trend
Best time to fly from ONT to SFO
Aim for departures around 6 a.m. (92% on-time); avoid 11 a.m. departures (42%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 68% | 24 min |
| Tuesdaybest | 82% | 11 min |
| Wednesday | 79% | 14 min |
| Thursday | 73% | 21 min |
| Friday | 73% | 17 min |
| Saturday | 81% | 20 min |
| Sunday | 70% | 18 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft29%
- Airline operations21%
- National airspace system46%
- Weather4%
Frequently asked questions
- How often are flights from ONT to SFO delayed?
- 25% of ONT–SFO flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-06 and 2026-05. The average arrival delay across completed flights was 18 minutes.
- Which airline is most reliable from ONT to SFO?
- SkyWest Airlines has the best on-time record on this route at 78%, based on 889 flights. 3 airlines flew ONT–SFO frequently enough to compare in this period.
- What is the best time of day to fly from ONT to SFO?
- Departures around 6 a.m. have the best record (92% on-time), while departures around 11 a.m. have the worst (42%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from ONT to SFO?
- The scheduled ONT–SFO flight time averages 1h 30m over 363 miles. Actual arrival times vary — flights on this route land 15+ minutes late 25% of the time.
- How often are ONT to SFO flights cancelled?
- 1.2% of scheduled flights on this route were cancelled between 2024-06 and 2026-05, at or below the national rate of 1.6%.
- What is the worst month to fly from ONT to SFO?
- May 2026 was the roughest month in this dataset, with only 43% of arrivals on time. The best was March 2026 at 91%. If your dates are flexible, that 48-point gap is worth planning around.
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Based on 2,869 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.