Best Time to Fly ONT to SFO: On-Time Stats by Hour & Airline
Ontario International → San Francisco International
Data through July 2026 · Last updated October 18, 2026
Over the last 12 months, 62.2% of Ontario (ONT) to San Francisco (SFO) flights arrived on time (1,309 scheduled flights). That is 15.5 points below the national average of 77.6%.
United Airlines was the most punctual of the 3 airlines on the route at 69.5%, while Frontier Airlines trailed at 38.7%.
January has been the best month (87% on time) and Monday the weakest day of the week (65%).
0.8% of flights were cancelled, versus 1.8% nationally.
ONT to SFO on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| United Airlines | 69.5% | 65 min | 0.4% | 981 |
| SkyWest Airlines | 41.5% | 61 min | 1.5% | 132 |
| Frontier Airlines | 38.7% | 68 min | 2.5% | 196 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly ONT to SFO
On-time arrival % by scheduled departure hour (local time), 2,899 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 5am–6am | Limited data | 12 | |
| 6am–7am | 91.7% | 0.6% | 679 |
| 7am–8am | 84.1% | 0.0% | 63 |
| 8am–9am | 44.8% | 2.5% | 119 |
| 9am–10am | 51.1% | 0.0% | 45 |
| 10am–11am | 70.6% | 0.8% | 255 |
| 11am–12pm | 36.7% | 0.0% | 30 |
| 12pm–1pm | Limited data | 3 | |
| 1pm–2pm | 74.0% | 0.4% | 550 |
| 2pm–3pm | 77.6% | 0.0% | 67 |
| 3pm–4pm | 81.2% | 2.4% | 164 |
| 4pm–5pm | 53.1% | 0.0% | 32 |
| 6pm–7pm | 60.1% | 1.4% | 646 |
| 7pm–8pm | 73.1% | 5.5% | 55 |
| 8pm–9pm | 14.3% | 0.0% | 49 |
| 9pm–10pm | 59.7% | 2.5% | 79 |
| 10pm–11pm | 57.1% | 3.9% | 51 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on ONT to SFO
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | 79.7% | +5.9 pts | 0.0% | 69 |
| Christmas & New Year (Dec 20 - Jan 3) | 60.5% | -13.3 pts | 2.7% | 112 |
| Summer peak (Jun 15 - Aug 15) | 62.5% | -11.3 pts | 0.7% | 462 |
| All other days | 73.8% | — | 1.1% | 2,256 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).