Best time to fly out of Ontario (ONT)
The early-flight folk wisdom holds up at Ontario: departures in the Before 6am band left on time 93% of the time, against 70.6% in the 8–10pm band. These are historical odds, not forecasts. The records say what happened on this schedule over three years; they know nothing about tomorrow’s thunderstorm.
Data through June 2026 · Bureau of Transportation Statistics
On-time rate by hour and day
On this page, “on time” means a departure that pushed back less than 15 minutes behind its scheduled time — the Bureau of Transportation Statistics definition, and the one airlines are held to.
| Departure time | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Before 6am | 90 | 92 | 92 | 95 | 93 | 94 | 94 |
| 6–8am | 92 | 94 | 93 | 94 | 94 | 93 | 93 |
| 8–10am | 89 | 90 | 92 | 93 | 91 | 90 | 90 |
| 10am–12pm | 82 | 87 | 84 | 83 | 85 | 84 | 83 |
| 12–2pm | 76 | 81 | 83 | 78 | 76 | 82 | 77 |
| 2–4pm | 71 | 77 | 77 | 72 | 66 | 77 | 67 |
| 4–6pm | 75 | 83 | 81 | 73 | 71 | 83 | 71 |
| 6–8pm | 74 | 82 | 80 | 73 | 71 | 76 | 67 |
| 8–10pm | 75 | 79 | 73 | 69 | 67 | 76 | 63 |
| 10pm–12am | 81 | 80 | 84 | 81 | 80 | 76 | 80 |
The steadiest stretch at ONT was Before 6am — 93% of departures left on time across 5,365 flights. The weakest was 8–10pm at 70.6%. 6–8am departures from ONT left on time 93% of the time across 15,056 flights; 6–8pm departures, 74.2% across 6,823. That is a gap of 18.8 points, and it is the whole case for the early flight.
The year at ONT
June was the hard month at ONT: 77.5% of departures left on time, across 6,915 flights. February was the easy one at 85.6%. Each month pools three years of that month, so a single bad week does not decide it.
| Month | Share departures that left on time | Flights |
|---|---|---|
| January | 84.3% | 5,721 |
| February | 85.6% | 5,239 |
| March | 83.7% | 6,210 |
| April | 83.3% | 6,467 |
| May | 80.3% | 6,897 |
| June | 77.5% | 6,915 |
| July | 79% | 6,942 |
| August | 82.2% | 6,920 |
| September | 85.2% | 6,571 |
| October | 84.9% | 6,868 |
| November | 85.1% | 6,490 |
| December | 83.8% | 6,332 |
Airlines at ONT
Every airline with at least 100 departures from ONT, busiest first. These are that airline’s departures from this airport only — its record across the country sits on its own page.
| Airline | Left on time | Typical delay | Cancelled | Departures |
|---|---|---|---|---|
| Southwest Airlines | 81.5% | 50 min | 0.5% | 34,335 |
| American Airlines | 82.7% | 103 min | 1.5% | 10,341 |
| Frontier Airlines | 76.8% | 86 min | 1.8% | 8,334 |
| SkyWest Airlines | 88.6% | 78 min | 0.4% | 6,861 |
| Delta Air Lines | 90% | 81 min | 1.2% | 5,611 |
| United Airlines | 83.8% | 72 min | 0.6% | 5,489 |
| Alaska Airlines | 85.2% | 56 min | 1.7% | 4,928 |
| Hawaiian Airlines | 88.6% | 73 min | 0.6% | 715 |
| JetBlue Airways | 69.9% | 123 min | 2.3% | 711 |
| Envoy Air | 94.3% | — | 0% | 247 |
A dash under typical delay means fewer than 30 of that airline’s departures ran 15 minutes late or more — too few to average.
What delays out of ONT were put down to
Airlines file a reason with every arrival running 15 minutes late or more. Across 12,522 flights that departed ONT and ran 15 minutes late or more, the delay minutes break down with 45.3% put down to late-arriving aircraft and 32.9% to airline operations.
- Late-arriving aircraft 45.3%
- Airline operations 32.9%
- Air traffic & airport volume 19.5%
- Severe weather 2.2%
- Security 0.1%
Late-arriving aircraft is the knock-on category: the plane came in late, so it went out late again. It is why a 7am problem in Newark is still a problem in Denver at dinnertime, and why it is usually the biggest slice on the bar.
If you are connecting through ONT
Of 77,572 scheduled arrivals into ONT, 78.3% reached the gate less than 15 minutes behind schedule. Of the 16,119 arrivals that ran late, 58.7% were no more than 45 minutes behind — which is the difference between a tight connection and a new boarding pass.
Work out a specific layover — pick the airport and the minutes you have, and the tool reads the same arrival records back as a share.
Busiest routes out of ONT
Ranked by flights, with the share that arrived on time at the far end. Where a route carries enough flights for a page of its own the chip goes there; otherwise it goes to the destination airport.
- PHX 85.2% on time · 9,475 flights
- DEN 82.4% on time · 8,431 flights
- LAS 78.1% on time · 7,978 flights
- SEA 86.5% on time · 7,496 flights
- DFW 80% on time · 7,076 flights
- SMF 87% on time · 5,967 flights
- OAK 87% on time · 4,695 flights
- SFO 72.1% on time · 4,307 flights
- SJC 87% on time · 4,120 flights
- SLC 91.9% on time · 3,610 flights
ONT in one number
Ontario (ONT)
Rank 56 of 363 US airports by departures. Steadiest stretch of the day: Before 6am. Hardest month: June.
Questions about ONT
- What is the best time of day to fly out of Ontario?
- Before 6am. Departures in that band left on time 93% of the time across 5,365 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 8–10pm band was the weakest at 70.6%.
- Is the early flight out of ONT really more reliable?
- 6–8am departures from ONT left on time 93% of the time across 15,056 flights; 6–8pm departures, 74.2% across 6,823. That is a gap of 18.8 points, and it is the whole case for the early flight.
- What is the worst month to fly out of ONT?
- June: 77.5% of the departures that flew left on time, with 6,915 scheduled. February was the other end of the year at 85.6%. Each figure pools three years of that calendar month.
- Which airline is most on time at ONT?
- Envoy Air — 94.3% of its 247 departures from ONT left on time. JetBlue Airways sat at the other end at 69.9% over 711 flights. Only airlines with at least 100 departures here are ranked.
- How often are flights cancelled at ONT?
- 0.9% of scheduled departures were cancelled over July 2023 through June 2026. Cancellations are counted against everything scheduled, not against everything that flew — a rate that looks small still adds up to real people in a rebooking line.