Route profile
ONT→SFO
Flight reliability, delays and best times to fly from Ontario to San Francisco, 363 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 26% of comparable major US routes (4,598 compared)
Calculated from 4,430 flights. How this is calculated
ONT → SFO arrives on time 71.4% of the time; the return trip, SFO → ONT, arrives on time 80.5% of the time, a 9.1-point gap between the two directions of the same city pair.
ONT → SFO spends 29.2 minutes on the ground on a 363-mile trip: 21.4 minutes from pushback to wheels-up at ONT and 7.8 minutes from touchdown to gate at SFO.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Reliability on this route has fallen unusually sharply over the past year, a bigger swing than 99% of 5,368 comparable routes.
62.2% on time over the most recent 12 months (2025-08 to 2026-07), against 79.5% in the 12 months before (2024-08 to 2025-07), a change of 17.3 points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 5,368 in the comparison.
What sets this route apart
Where ONT to SFO differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
ONT to SFO struggles most at 8 AM: 46.4% of its flights scheduled then arrive on time, 40.1 points behind the 86.5% on routes of similar length at the same hour. Against all other routes the gap is 39.5 points.
Monday is the day ONT to SFO slips furthest against routes of similar length, 63.9% on time where they average 78.2%, 14.3 points lower. Against all other routes the gap is 13.4 points.
In May, ONT to SFO runs 17.1 points below routes of similar length, 59.5% on time to 76.6%. Against all other routes the gap is 15.8 points.
Frontier Airlines’ flights on ONT to SFO arrive on time 54.9% of the time, 16.4 points below the 71.3% it manages on its routes of similar length. Against all other routes the gap is 16.4 points.
ONT to SFO against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 8 AM departures | 46.4% | routes of similar length | 86.5% | −40.1 pts | 252 here, 106,052 there |
| Weekday: Monday | 63.9% | routes of similar length | 78.2% | −14.3 pts | 685 here, 226,061 there |
| Month: May | 59.5% | routes of similar length | 76.6% | −17.1 pts | 348 here, 127,413 there |
| Airline: Frontier Airlines | 54.9% | routes of similar length | 71.3% | −16.4 pts | 818 here, 50,446 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 363 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
When it goes wrong
July 2023 – July 2026
56 min late
against a median of 4 min early
ONT → SFO has an average that understates its risk: a typical arrival is 4 min early, but the worst tenth are 60 minutes worse than that. If the trip has something unmissable at the end of it, the median is the wrong number to plan against.
Percentiles over 4,430 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SFO after arriving from ONT.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 43% | Likely to miss |
| 45 min | 28% | High risk |
| 60 min | 19% | High risk |
| 90 min | 8.9% | Some risk |
| 120 min | 5.0% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.04% of the time and diverts 0.07% of the time, which a late arrival never shows up in.
Chance of missing is the share of 4,381 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 56 minutes late (90th-percentile gate arrival delay), over 4,430 operations.
Any other layover length: connection checker.
Best time to fly
ONT → SFO flights departing 5–9 AM arrived on time 79.6% of the time, against 58.7% for 9 PM–5 AM departures, a gap of 20.9 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 91.5% on time from 972 flights
- 7 AM: 53.0% on time from 133 flights
- 8 AM: 46.4% on time from 256 flights
- 9 AM: too few flights to score
- 10 AM: 67.0% on time from 592 flights
- 11 AM to 12 PM: too few flights to score
- 1 PM: 74.3% on time from 619 flights
- 2 PM: too few flights to score
- 3 PM: 78.1% on time from 187 flights
- 4 PM: 73.5% on time from 226 flights
- 5 PM: too few flights to score
- 6 PM: 61.2% on time from 763 flights
- 7 PM: too few flights to score
- 8 PM: 64.0% on time from 173 flights
- 9 PM to 11 PM: too few flights to score
Why ONT → SFO runs late
July 2023 – July 2026
airspace and airport capacity, including weather-driven flow control
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
weather severe enough to stop this flight specifically
Share of the delay minutes US DOT attributed to each cause for ONT → SFO. Only delays of 15 minutes or more are attributed.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 1,918 | 76.5% | 0.47% | -6 min | 6.6% |
| SkyWest Airlines | 1,677 | 73.6% | 1.19% | -5 min | 9.6% |
| Frontier Airlines | 835 | 54.9% | 2.04% | 9 min | 14.7% |
United Airlines flew 43.3% of the 4,430 flights listed. Frontier Airlines cancelled 2.04% of its flights here against 0.47% for United Airlines.
United Airlines arrived on time 21.6 percentage points more often than Frontier Airlines on this route.
Other ways to fly Los Angeles to San Francisco
Airport pairs in the same two city markets, as the DOT defines them.
| Route | Flights | On time | Cancelled | Median delay | Score |
|---|---|---|---|---|---|
| LAX→SFO Los Angeles to San Francisco | 34,819 | 69.3% | 0.67% | -1 min | 55 |
| LAX→SJC Los Angeles to San Jose | 15,597 | 86.5% | 0.35% | -9 min | 87 |
| SNA→SFO Santa Ana to San Francisco | 13,797 | 71.6% | 1.26% | -3 min | 54 |
| ONT→SFO this route Ontario to San Francisco | 4,430 | 71.4% | 1.04% | -4 min | 56 |
LAX → SJC is the most reliable pairing for this journey at 86.5% on time, against 71.6% for SNA → SFO.
Flying to SFO from the Los Angeles area? Compare ONT, LAX, SNA, BUR for SFO, with the same test for what counts as a real difference.
Weekly and seasonal patterns
By day of week
Saturday is historically the most reliable day and Monday the least, a gap of 13.7 percentage points.
By month
- Jan: 82.4%
- Feb: 72.5%
- Mar: 71.0%
- Apr: 67.8%
- May: 59.5%
- Jun: 58.3%
- Jul: 70.5%
- Aug: 74.3%
- Sep: 72.4%
- Oct: 75.9%
- Nov: 75.9%
- Dec: 74.2%
June is historically the weakest month and January the strongest, a spread of 24.1 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 80.4% from 138 flights
- August 2023: 74.1% from 120 flights
- September 2023: 69.4% from 134 flights
- October 2023: 84.0% from 163 flights
- November 2023: 79.6% from 147 flights
- December 2023: too few flights to score (118)
- January 2024: too few flights to score (98)
- February 2024: too few flights to score (98)
- March 2024: 55.0% from 120 flights
- April 2024: too few flights to score (90)
- May 2024: too few flights to score (92)
- June 2024: too few flights to score (86)
- July 2024: 81.5% from 127 flights
- August 2024: 76.8% from 140 flights
- September 2024: 80.5% from 149 flights
- October 2024: 80.5% from 165 flights
- November 2024: 73.0% from 180 flights
- December 2024: 73.2% from 140 flights
- January 2025: too few flights to score (101)
- February 2025: too few flights to score (105)
- March 2025: too few flights to score (117)
- April 2025: 86.9% from 154 flights
- May 2025: 83.2% from 131 flights
- June 2025: too few flights to score (104)
- July 2025: too few flights to score (104)
- August 2025: too few flights to score (109)
- September 2025: too few flights to score (108)
- October 2025: too few flights to score (114)
- November 2025: too few flights to score (105)
- December 2025: too few flights to score (104)
- January 2026: too few flights to score (93)
- February 2026: too few flights to score (79)
- March 2026: too few flights to score (103)
- April 2026: 53.2% from 124 flights
- May 2026: 43.2% from 127 flights
- June 2026: 33.3% from 120 flights
- July 2026: 44.3% from 123 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 62.2% against 79.5% in the 12 months before — declining by 17.3 percentage points.
Data and methodology
Calculated by FlyerIntel from 4,430 ONT → SFO flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed