Route profile
SJC→ONT
Flight reliability, delays and best times to fly from San Jose to Ontario, 333 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 94% of comparable major US routes (4,598 compared)
Calculated from 4,233 flights. How this is calculated
SJC → ONT arrives on time 84.8% of the time; the return trip, ONT → SJC, arrives on time 86.8% of the time, a 2.0-point gap between the two directions of the same city pair.
SJC → ONT spends 16.1 minutes on the ground on a 333-mile trip: 11.5 minutes from pushback to wheels-up at SJC and 4.6 minutes from touchdown to gate at ONT.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
On-time performance swings unusually widely by time of day here, wider than 100% of 4,023 comparable routes.
97.4% on time for 5–9 AM departures, against 52.1% for 9 PM–5 AM.
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 4,023 in the comparison.
What sets this route apart
Where SJC to ONT differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
SJC to ONT struggles most at 9 PM: 51.7% of its flights scheduled then arrive on time, 19.1 points behind the 70.8% on routes of similar length at the same hour. Against all other routes the gap is 17.8 points.
SJC to ONT is at its best against routes of similar length for flights scheduled at 12 PM: 93.8% arrive on time, 12.4 points ahead of the 81.4% those routes manage at that hour. Against all other routes the gap is 14.4 points.
SJC to ONT holds up on Tuesdays better than routes of similar length do: 89.9% on time to their 84.0%, a 5.9 points lead. Against all other routes the gap is 8.3 points.
April is kinder to SJC to ONT than to routes of similar length: 88.3% on time against 80.8%, 7.5 points better. Against all other routes the gap is 8.4 points.
Southwest Airlines does better on SJC to ONT than on its routes of similar length: 84.8% on time here, 81.1% there, 3.7 points apart. Against all other routes the gap is 7.4 points.
SJC to ONT against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 9 PM departures | 51.7% | routes of similar length | 70.8% | −19.1 pts | 120 here, 34,230 there |
| Hour: 12 PM departures | 93.8% | routes of similar length | 81.4% | +12.4 pts | 130 here, 55,268 there |
| Weekday: Tuesday | 89.9% | routes of similar length | 84.0% | +5.9 pts | 576 here, 149,146 there |
| Month: April | 88.3% | routes of similar length | 80.8% | +7.5 pts | 324 here, 87,643 there |
| Airline: Southwest Airlines | 84.8% | routes of similar length | 81.1% | +3.7 pts | 4,213 here, 359,996 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 333 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
26 min late
against a median of 8 min early
Percentiles over 4,233 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at ONT after arriving from SJC.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 28% | High risk |
| 45 min | 15% | Some risk |
| 60 min | 8.7% | Some risk |
| 90 min | 3.8% | Low risk |
| 120 min | 1.8% | 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 0.40% 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 4,213 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 26 minutes late (90th-percentile gate arrival delay), over 4,233 operations.
Any other layover length: connection checker.
Best time to fly
SJC → ONT flights departing 5–9 AM arrived on time 97.4% of the time, against 52.1% for 9 PM–5 AM departures, a gap of 45.3 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 97.7% on time from 346 flights
- 7 AM: 97.2% on time from 475 flights
- 8 AM: 97.2% on time from 250 flights
- 9 AM: 92.3% on time from 169 flights
- 10 AM: 93.5% on time from 323 flights
- 11 AM: 88.6% on time from 333 flights
- 12 PM: 93.8% on time from 131 flights
- 1 PM: 80.5% on time from 196 flights
- 2 PM: 88.1% on time from 135 flights
- 3 PM: 77.9% on time from 146 flights
- 4 PM: 79.3% on time from 261 flights
- 5 PM: 72.7% on time from 319 flights
- 6 PM: 80.9% on time from 268 flights
- 7 PM: 82.5% on time from 219 flights
- 8 PM: 70.4% on time from 539 flights
- 9 PM: 51.7% on time from 122 flights
- 10 PM to 11 PM: too few flights to score
Why SJC → ONT runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
Share of the delay minutes US DOT attributed to each cause for SJC → ONT. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on SJC → ONT, at 70.8%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 97.4% of the time and 9 PM–5 AM departures 52.1%.
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 4,233 | 84.8% | 0.40% | -8 min | 3.9% |
Other ways to fly San Francisco to Los Angeles
Airport pairs in the same two city markets, as the DOT defines them.
| Route | Flights | On time | Cancelled | Median delay | Score |
|---|---|---|---|---|---|
| SFO→LAX San Francisco to Los Angeles | 34,804 | 77.1% | 0.70% | -5 min | 67 |
| SJC→LAX San Jose to Los Angeles | 15,614 | 86.7% | 0.37% | -10 min | 88 |
| SFO→SNA San Francisco to Santa Ana | 13,715 | 80.2% | 1.13% | -6 min | 72 |
| SJC→ONT this route San Jose to Ontario | 4,233 | 84.8% | 0.40% | -8 min | 85 |
SJC → LAX is the most reliable pairing for this journey at 86.7% on time, against 77.1% for SFO → LAX.
Flying to ONT from the San Francisco area? Compare SJC, SFO, OAK for ONT, with the same test for what counts as a real difference.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 11.6 percentage points.
By month
- Jan: 88.6%
- Feb: 89.9%
- Mar: 85.4%
- Apr: 88.3%
- May: 84.5%
- Jun: 77.3%
- Jul: 77.6%
- Aug: 84.3%
- Sep: 86.4%
- Oct: 82.0%
- Nov: 90.7%
- Dec: 86.9%
June is historically the weakest month and November the strongest, a spread of 13.4 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 77.4% from 135 flights
- August 2023: 76.3% from 143 flights
- September 2023: 87.7% from 131 flights
- October 2023: 85.0% from 134 flights
- November 2023: too few flights to score (119)
- December 2023: 89.4% from 123 flights
- January 2024: too few flights to score (110)
- February 2024: too few flights to score (99)
- March 2024: too few flights to score (102)
- April 2024: too few flights to score (104)
- May 2024: too few flights to score (108)
- June 2024: too few flights to score (115)
- July 2024: too few flights to score (116)
- August 2024: 92.5% from 134 flights
- September 2024: 86.4% from 132 flights
- October 2024: 87.8% from 123 flights
- November 2024: too few flights to score (110)
- December 2024: too few flights to score (110)
- January 2025: too few flights to score (101)
- February 2025: too few flights to score (91)
- March 2025: too few flights to score (106)
- April 2025: too few flights to score (114)
- May 2025: 87.8% from 123 flights
- June 2025: too few flights to score (115)
- July 2025: too few flights to score (118)
- August 2025: too few flights to score (110)
- September 2025: too few flights to score (107)
- October 2025: too few flights to score (110)
- November 2025: too few flights to score (116)
- December 2025: too few flights to score (118)
- January 2026: too few flights to score (101)
- February 2026: too few flights to score (99)
- March 2026: too few flights to score (107)
- April 2026: too few flights to score (106)
- May 2026: too few flights to score (110)
- June 2026: too few flights to score (114)
- July 2026: too few flights to score (119)
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 82.5% against 88.0% in the 12 months before — declining by 5.5 percentage points.
Data and methodology
Calculated by FlyerIntel from 4,233 SJC → ONT 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