Routes › Ontario (ONT) › ONT to SFO
Route · 12 months to July 2026
Ontario to San Francisco: on-time record
Ontario International to San Francisco International
BTS: A flight is counted as on time if it arrived less than 15 minutes after its scheduled time. Only carriers with at least 0.5 percent of domestic scheduled passenger revenue report. Data through July 2026; this is a monthly history, not live flight status.
61.7% of scheduled ONT to SFO flights arrived on time in the 12 months to July 2026. The figure covers 1,309 flights between Ontario and San Francisco by carriers that report to BTS, a distance of 363 miles.
That is 14.3 points below the national on-time share of 76.0% for the same period and 19.5 points below the 81.2% recorded for all departures from ONT. Flights that did arrive were 19.3 min late on average, and 0.8% of scheduled flights were cancelled (national: 1.8%).
3 reporting carriers flew the route at least 60 times. United Airlines had the highest on-time share at 69.2% of 981 flights; Frontier Airlines had the lowest at 37.8% of 196.
By scheduled departure hour (local time at ONT), flights leaving from 6 am to 7 am had the highest on-time share, 90.5%; those leaving from 8 pm to 9 pm had the lowest, 14.3%.
The on-time share is down 16.7 points on the previous 12 months (78.4%); cancellations moved from 1.3% to 0.8%.
Of the delay minutes that carriers assigned to a BTS cause category on this route, national aviation system 59%, late-arriving aircraft 24% and air carrier 15%.
- On time 61.7%
- Arrived 15+ minutes late 37.5%
- Cancelled 0.8%
- Diverted 0.0%
Airlines on the route compared
| Reporting carrier | Flights | Share | On time | Avg arrival delay | Cancelled |
|---|---|---|---|---|---|
| UA United Airlines | 981 | 75% | 69.2% | 14.2 min | 0.4% |
| F9 Frontier Airlines | 196 | 15% | 37.8% | 37.9 min | 2.6% |
| OO SkyWest Airlines | 132 | 10% | 40.9% | 30.5 min | 1.5% |
Carriers with at least 24 flights in the 12 months to July 2026. The on-time pill is green when a carrier is at or above the route's overall share. Regional carriers operate flights sold under larger airlines' brands; BTS lists the carrier that operated the flight.
Compared with the airports and the nation
| Measure | ONT to SFO | All departures from ONT | All arrivals at SFO | All reported flights |
|---|---|---|---|---|
| Arrived on time | 61.7% | 81.2% | 67.2% | 76.0% |
| Arrived 15+ minutes late | 37.5% | 17.7% | 31.6% | 21.9% |
| Cancelled | 0.8% | 0.9% | 1.1% | 1.8% |
| Diverted | 0.0% | 0.2% | 0.2% | 0.3% |
| Average arrival delay | 19.3 min | 4.0 min | 14.0 min | 8.1 min |
| Delay minutes per 100 flights | 2,552 | 1,296 | 2,198 | 1,684 |
| Scheduled flights | 1,309 | 25,854 | 147,716 | 7,043,858 |
12 months to July 2026. Delay minutes count late arrivals only (an early arrival is zero), so the per-100-flights row is a normalised total rather than an average of early and late.
The return direction, SFO to ONT, recorded 75.7% on time across 1,310 flights in the same period.
Month by month
Year on year: on time 61.7% against 78.4% (−16.7 pts), cancelled 0.8% against 1.3%, flights 1,309 against 1,590.
By scheduled departure hour
Delay causes
Seasonality
| Calendar month | Flights | On time | Cancelled | Avg arrival delay | Years in sample |
|---|---|---|---|---|---|
| Jan | 292 | 81.8% | 0.7% | 8.1 min | 3 |
| Feb | 282 | 70.2% | 3.2% | 10.1 min | 3 |
| Mar | 340 | 69.7% | 1.5% | 10.5 min | 3 |
| Apr | 368 | 67.7% | 0.3% | 8.7 min | 3 |
| May | 350 | 59.1% | 0.6% | 17.6 min | 3 |
| Jun | 310 | 57.7% | 1.0% | 22.7 min | 3 |
| Jul | 354 | 65.8% | 1.1% | 13.5 min | 3 |
| Aug | 369 | 72.9% | 1.9% | 8.5 min | 3 |
| Sep | 391 | 72.4% | 0.0% | 9.3 min | 3 |
| Oct | 442 | 75.6% | 0.2% | 10.3 min | 3 |
| Nov | 432 | 74.5% | 1.6% | 13.5 min | 3 |
| Dec | 362 | 73.2% | 1.4% | 10.4 min | 3 |
Each calendar month summed across the 36 months on file, so most rows combine three years. The pill compares the month with the route's own 12-month share.
Other routes from Ontario (ONT)
| Route | Cities | Flights | On time | Avg arrival delay | Cancelled |
|---|---|---|---|---|---|
| ONT–PHX | Ontario to Phoenix | 3,027 | 82.0% | 5.6 min | 0.6% |
| ONT–DEN | Ontario to Denver | 2,643 | 80.6% | 5.7 min | 0.3% |
| ONT–SEA | Ontario to Seattle | 2,505 | 85.3% | -1.3 min | 1.1% |
| ONT–LAS | Ontario to Las Vegas | 2,476 | 76.3% | 7.2 min | 0.9% |
| ONT–DFW | Ontario to Dallas/Fort Worth | 2,297 | 76.5% | 11.1 min | 2.7% |
| ONT–SMF | Ontario to Sacramento | 2,114 | 85.3% | -1.6 min | 0.3% |
| ONT–OAK | Ontario to Oakland | 1,471 | 86.1% | -2.4 min | 0.4% |
| ONT–SJC | Ontario to San Jose | 1,319 | 85.4% | -0.7 min | 0.1% |
All 25 routes and the airport record for ONT · airport record for SFO
Questions and answers
How often are flights from Ontario to San Francisco on time?
61.7% of the 1,309 flights scheduled from ONT to SFO in the 12 months to July 2026 arrived less than 15 minutes after their scheduled time. The national share for the same period was 76.0%. Cancelled and diverted flights count as not on time.
Which airline has the highest on-time share from ONT to SFO?
Among reporting carriers with at least 60 flights on the route, United Airlines had the highest on-time share (69.2%), followed by SkyWest Airlines (40.9%) and Frontier Airlines (37.8%). Differences of a point or two on a few hundred flights are small.
What causes delays between Ontario and San Francisco?
For flights that arrived 15 or more minutes late, carriers attributed the delay minutes as follows: national aviation system 59%, late-arriving aircraft 24%, air carrier 15%, extreme weather 3%, security 0%. The categories are the carriers' own reports to BTS; weather that slows the wider system is usually recorded under the National Aviation System rather than extreme weather.
What time of day has the highest on-time share from ONT?
Flights scheduled to leave ONT from 6 am to 7 am arrived on time 90.5% of the time, the highest of any hour with enough flights to compare. The lowest was 8 pm to 9 pm at 14.3%. Delays tend to build through the day as late aircraft carry over to later flights.
Is it getting better?
The on-time share for the 12 months to July 2026 was 61.7%, down 16.7 points on the previous 12 months (78.4%). The monthly chart on this page shows each of the last 36 months. Across those months, January had the highest on-time share (81.8%) and June the lowest (57.7%).
Where does this data come from?
Every figure is computed from the Bureau of Transportation Statistics Reporting Carrier On-Time Performance files, which list each scheduled domestic flight by the carriers required to report. This page covers August 2023 to July 2026. It shows totals and averages only; it is not a live flight-status service.
Provenance
Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance (1987 to present), monthly files August 2023 to July 2026, a US government work in the public domain. Figures are totals and averages over all scheduled flights by reporting carriers on the route; no individual flight or aircraft is identified. Times are local to the departure airport. The load factor and passenger counts from the BTS T-100 series are not included in this edition. See the methodology; report processing errors through corrections.