Route reliability record
ONT→SJC
Ontario to San Jose
- Flights
- 1,320
- Period
- September 2025 to August 2026
- Distance
- 333 mi
- Carriers
- 1
This route earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 1,320 ONT to SJC flights, with a median arrival 10 minutes early.
Best time to fly ONT to SJC: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 98.0% of the time and Tuesday flights 92.0%, against 85.9% for the route overall.
Set against the rest of the country, this route's record is 9 points better than the US average of 77.3%. That gap is worth roughly 86 fewer late arrivals for every thousand flights.
Key figures
On time
85.9%
Arrivals under 15 minutes late, of 1,319 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.08%
National rate is 1.89%
Best carrier
Southwest
85.9% on time across 1,320 flights
These figures cover 1,320 flights between September 2025 and August 2026. The median arrival is 10 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Carrier by carrier
Which airline is most reliable on ONT to SJC
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 1,320 | 85.9% | 57 min | 0.08% | A+ |
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Best ways to make this trip
The most reliable ways to fly Ontario to San Jose
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. LAX → SJCLos Angeles to San Jose | SkyWest Airlines | 90.3% | 90.7% | 0.39% | 8am–11am, Tue | OO 3883 18:00 |
| 2. LAX → MRYLos Angeles to Monterey | SkyWest Airlines | 89.7% | 90.3% | 0.70% | 2pm–5pm, Tue | — |
| 3. LGB → OAKLong Beach to Oakland | Southwest Airlines | 88.1% | 88.5% | 0.45% | 5am–8am, Tue | — |
| 4. ONT → SJCOntario to San Jose | Southwest Airlines | 85.8% | 85.9% | 0.08% | 5am–8am, Tue | — |
| 5. LGB → SJCLong Beach to San Jose | Southwest Airlines | 85.8% | 86.0% | 0.24% | 8am–11am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 32 points, against half a point between the best and worst carrier.
- 5am–8am253 flights98.0%
- 8am–11am240 flights94.6%
- 11am–2pm185 flights92.4%
- 2pm–5pm247 flights80.6%
- 5pm–8pm276 flights76.1%
- 8pm–5am119 flights66.4%
Scale runs 60% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 98.0% of the time, against 66.4% for the overnight window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 276 flights scheduled in it.
Explore
Filter ONT to SJC by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On ONT to SJC, the best departure window is 5am–8am at 98.0% on time and the worst is 8pm–5am at 66.4%, a wide gap of 31.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am98.0%
- 8–11am94.6%
- 11am–2pm92.4%
- 2–5pm80.6%
- 5–8pm76.1%
- 8pm–5am66.4%
best all US flightsScale 60% to 100%.
Across the year
When delays peak on this route
This route's year swings by 19 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 75.4% on time, 19 points below January, the best at 94.1%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 119 flights.
Across the week, Tuesday is the strongest day at 92.0% on time and Sunday the weakest at 79.2%, a spread of 13 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 80% of the 11,000 delay minutes carriers reported here, and the remaining four split what is left.
- 80%Late-arriving aircraft
- 19%Carrier
- 2%National Airspace System
- 0%Security
80% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 11,000 reported delay minutes here, that single category outweighs weather by 80 to one. The split is drawn from 10,513 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 98.0% on time here.
Cancellations are rare at 0.08%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.3% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
At 333 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 82.4% on time across 1,318 flights, 4 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 4 points of difference.
The sample behind these figures is 1,320 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in SJC after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 94.1% on time and June 75.4%, a swing of 19 points. If the dates move at all, move them out of June before you think about anything else. 1,319 completed flights over 12 months sit behind that.
Common questions
ONT to SJC questions
How often is ONT to SJC delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 14.1% of the 1,320 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is ONT to SJC compared with the rest of the country?
85.9% of flights arrive on time here against a national 77.3%, a difference of 9 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on ONT to SJC?
The 5am–8am departure window is the strongest at 98.0% on time. The 8pm–5am window is the weakest at 66.4%, 32 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on ONT to SJC?
June is the weakest month at 75.4% on time, compared with 94.1% in January. Across the year that is 19 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SJC to ONT — the return legseparate record
- Ontario International (ONT) delay statistics
- Norman Y. Mineta San Jose International (SJC) delay statistics
- ONT to PHX, a related route82.4%
- SAN to SJC, a related route74.5%
- ONT to DEN, a related route81.8%
- Southwest Airlines on-time record85.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. ONT to SJC and SJC to ONT are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.