Route reliability record
OAK→ONT
Oakland to Ontario
- Flights
- 1,458
- Period
- September 2025 to August 2026
- Distance
- 362 mi
- Carriers
- 1
This route lands a B+, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That rests on 1,458 OAK to ONT flights, with a median arrival 7 minutes early.
Best time to fly OAK to ONT: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 97.6% of the time and Tuesday flights 83.4%, against 80.2% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.2%
Arrivals under 15 minutes late, of 1,450 completed flights
Avg delay
49 min
Across delayed arrivals only, not all flights
Cancelled
0.48%
National rate is 1.89%
Best carrier
Southwest
80.2% on time across 1,458 flights
These figures cover 1,458 flights between September 2025 and August 2026. The median arrival is 7 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 OAK to ONT
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 | 1,458 | 80.2% | 49 min | 0.48% | B+ |
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Best ways to make this trip
The most reliable ways to fly Oakland to Ontario
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. 5 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJC → LAXSan Jose to Los Angeles | SkyWest Airlines | 91.3% | 91.7% | 0.44% | 5am–8am, Tue | OO 3883 20:05 |
| 2. SJC → LAXSan Jose to Los Angeles | Delta Air Lines | 89.5% | 91.6% | 2.31% | 11am–2pm, Tue | — |
| 3. SJC → SNASan Jose to Santa Ana | Southwest Airlines | 85.9% | 86.6% | 0.78% | 5am–8am, Sat (route) | — |
| 4. OAK → LGBOakland to Long Beach | Southwest Airlines | 85.4% | 85.7% | 0.32% | 5am–8am, Tue | — |
| 5. SJC → LGBSan Jose to Long Beach | Southwest Airlines | 84.3% | 84.4% | 0.16% | 5am–8am, Wed | — |
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 44 points, against half a point between the best and worst carrier.
- 5am–8am337 flights97.6%
- 8am–11am207 flights92.3%
- 11am–2pm252 flights82.5%
- 2pm–5pm213 flights74.2%
- 5pm–8pm233 flights72.7%
- 8pm–5am216 flights53.2%
Scale runs 45% to 100%.
The 8pm–5am window is where this operation falls apart: 53.2% on time, against 97.6% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 337 flights scheduled in it.
Explore
Filter OAK to ONT 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 OAK to ONT, the best departure window is 5am–8am at 97.6% on time and the worst is 8pm–5am at 53.2%, a wide gap of 44.4 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am97.6%
- 8–11am92.3%
- 11am–2pm82.5%
- 2–5pm74.2%
- 5–8pm72.7%
- 8pm–5am53.2%
best all US flightsScale 45% to 100%.
Across the year
When delays peak on this route
This route's year swings by 25 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.
August is the worst month at 69.4% on time, 25 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. October was the busiest month here, with 136 flights.
Across the week, Tuesday is the strongest day at 83.4% on time and Thursday the weakest at 75.8%, a spread of 8 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 61% of the 14,000 delay minutes carriers reported here, and the remaining four split what is left.
- 61%Late-arriving aircraft
- 36%Carrier
- 4%National Airspace System
61% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 14,000 reported delay minutes here, that single category outweighs weather by 61 to one. The split is drawn from 13,956 reported delay minutes.
The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 5,000 of the 14,000 delay minutes reported here.
Cancellations are rare at 0.48%, 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 4.7% 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 362 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 86.0% on time across 1,450 flights, 6 points above 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 6 points of difference.
The sample behind these figures is 1,458 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 ONT 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 August 69.4%, a swing of 25 points. If the dates move at all, move them out of August before you think about anything else. 1,450 completed flights over 12 months sit behind that.
Common questions
OAK to ONT questions
How often is OAK to ONT delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.8% of the 1,458 flights in this analysis, against 22.7% nationally. Delayed flights are late by roughly 50 minutes on average.
How reliable is OAK to ONT compared with the rest of the country?
80.2% of flights arrive on time here against a national 77.3%, a difference of 3 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on OAK to ONT?
The 5am–8am departure window is the strongest at 97.6% on time. The 8pm–5am window is the weakest at 53.2%, 44 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 August delays on OAK to ONT?
August is the weakest month at 69.4% on time, compared with 94.1% in January. Across the year that is 25 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
- ONT to OAK — the return legseparate record
- Oakland International (OAK) delay statistics
- Ontario International (ONT) delay statistics
- OAK to SAN, a related route62.7%
- PHX to ONT, a related route76.8%
- OAK to LAS, a related route76.5%
- Southwest Airlines on-time record80.2%
- 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. OAK to ONT and ONT to OAK 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.