76% of flights from San Francisco to Ontario arrived on time over the past 12 months. That is worse than the typical U.S. route. The 10 a.m. departures ran on time 81% of the time; the 9 p.m. ones 73%. Most reliable airline: United Airlines (79%). 7% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for SFO → ONT: when a flight was late, it was under 45 minutes late 64% of the time. About 1 in 17 flights landed an hour or more late, and 1 in 103 three hours or more; 0.8% were cancelled outright.
- On time or early76%
- 15–30 min late10%
- 30–60 min late7.0%
- 1–2 hours late3.9%
- 2–3 hours late1.0%
- 3+ hours late1.0%
- Diverted0.0%
- Cancelled0.8%
Share of all 1,337 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| United Airlines | 1,126 | 79% | 0.5% | −4 min | 4.4% | +52 min | United Airlines 88%, SkyWest 12% |
| Frontier Airlines | 211 | 58% | 2.4% | +5 min | 14.2% | +77 min | Frontier Airlines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at SFO). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | United Airlines |
|---|---|
| 10 a.m. | 81% |
| 4 p.m. | 81% |
| 9 p.m. | 73% |
Last flight of the day
On SFO → ONT, each airline's last flight of the day was cancelled 0.8% of the time, against 0.4% for its earlier flights (2.1× as often). It arrived 3+ hours late 0.5% of the time (earlier flights: 0.8%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| United Airlines | 9:00 p.m. | 0.8% | 0.5% | 0.4% | first flight 10:40 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in ONT tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: October (86%). Worst: July (72%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 216 | 74% | 0.5% |
| Tuesday | 165 | 80% | 0.0% |
| Wednesday | 165 | 76% | 0.0% |
| Thursday | 196 | 73% | 1.5% |
| Friday | 211 | 72% | 0.9% |
| Saturday | 172 | 80% | 0.6% |
| Sunday | 212 | 78% | 1.9% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: airline 5 · weather 3 · air traffic/airport 3
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| F9 2678 | 9:33 a.m. | 211 | 58% | 2.4% | +5 min | Frontier Airlines |
| UA 2661 | 10:40 a.m. | 195 | 77% | 0.0% | 0 min | United Airlines |
| UA 552 | 9:30 p.m. | 216 | 80% | 0.5% | −4 min | United Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Jul 18, 2026 | 4 | 0% | 0 |
| Dec 26, 2025 | 4 | 0% | 0 |
| May 28, 2026 | 4 | 0% | 2 |
| Dec 22, 2025 | 4 | 0% | 0 |
| Nov 5, 2025 | 3 | 0% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of San Francisco or Ontario. SJC → SNA has been 10 points more reliable.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| SFO → ONT (this route) | 1,337 | 76% | 0.8% |
| SJC → SNA San Jose to Orange County John Wayne | 2,741 | 85% | 0.8% |
| OAK → LGB Oakland to Long Beach | 1,568 | 85% | 0.3% |
| SJC → LGB San Jose to Long Beach | 1,251 | 84% | 0.2% |
| SJC → LAX San Jose to Los Angeles LAX | 4,669 | 84% | 0.9% |
| OAK → SNA Oakland to Orange County John Wayne | 2,356 | 84% | 0.9% |
| SJC → BUR San Jose to Hollywood Burbank | 2,137 | 83% | 1.3% |
Questions
How often are flights from SFO to ONT on time?
76% of 1,337 scheduled flights from San Francisco, CA to Ontario, CA arrived within 15 minutes of schedule between September 2025 and August 2026. 0.8% were cancelled.
What is the best time of day to fly SFO to ONT?
Flights scheduled to leave at 10 a.m. were the most reliable (81% on time). The 9 p.m. departures were the least (73%).
Which airline is most on time from SFO to ONT?
United Airlines: 79% of its 1,126 flights on the route arrived on time. Frontier Airlines: 58%.
What month has the most delays from SFO to ONT?
July (72% on time). The best month is October (86%), over 2023–2026.
Is the last flight of the day from SFO to ONT more likely to be cancelled?
Yes. Each airline's last SFO–ONT flight of the day was cancelled 0.8% of the time over the past year, against 0.4% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- ONT → SFO (return)
- San Francisco (SFO) delays by hour
- Flights into Ontario (ONT)
- United Airlines on-time record
- Frontier Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.