Airport month record
ONTJUN
Ontario International in June 2026
- Departures
- 2,304
- Month
- June 2026
- National, same month
- 74.3%
- Carriers
- 8
Historical statistics for June 2026, not live status or a forecast for this year’s June. For today’s conditions at ONT, see live FAA status.
ONT in June lands a B, 2 points better than the national rate of 74.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 2,304 flights, with a median arrival 5 minutes early.
Key figures
On time
76.7%
Arrivals under 15 minutes late, of 2,273 completed departures
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
1.00%
Nationally in June: 1.65%
Whole year
81.9%
ONT across all twelve months
These figures cover 2,304 departures from Ontario International in June 2026. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.
Against the year
June next to ONT's other months
Against ONT's own year, June ran 5 points worse than the twelve-month rate of 81.9%, which makes it the worst of the twelve months in the data. Either side of it, May ran 80.0% on time and July 77.9%, so a trip moved by a few weeks would have landed in a better stretch.
| Month | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| September 2025 | 2,177 | 84.8% | 76 min | 0.51% | B+ |
| October 2025 | 2,265 | 81.6% | 64 min | 0.49% | B+ |
| November 2025 | 2,184 | 81.9% | 63 min | 2.06% | B |
| December 2025 | 2,132 | 82.4% | 70 min | 0.70% | B+ |
| January 2026 | 1,892 | 86.5% | 87 min | 1.69% | A |
| February 2026 | 1,734 | 87.8% | 70 min | 0.35% | A+ |
| March 2026 | 2,081 | 82.8% | 57 min | 1.01% | B |
| April 2026 | 2,119 | 82.8% | 61 min | 0.28% | B+ |
| May 2026 | 2,298 | 80.0% | 58 min | 0.70% | B+ |
| June 2026 (this page) | 2,304 | 76.7% | 66 min | 1.00% | B |
| July 2026 | 2,377 | 77.9% | 75 min | 0.88% | B+ |
| August 2026 | 2,228 | 80.9% | 70 min | 0.81% | B+ |
Departure window
The best time of day to leave ONT in June
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 40 points, against half a point between the best and worst carrier.
- 5am–8am560 flights94.4%
- 8am–11am339 flights83.4%
- 11am–2pm442 flights78.2%
- 2pm–5pm320 flights54.1%
- 5pm–8pm333 flights68.0%
- 8pm–5am310 flights67.8%
Scale runs 45% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.4% of the time, against 54.1% for the afternoon window. That is 40 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 560 flights scheduled in it.
Across the week, Tuesday is the strongest day at 81.4% on time and Sunday the weakest at 73.8%, a spread of 8 points.
Carrier by carrier
Which airlines ran best at ONT in June
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 | 1,007 | 73.3% | 47 min | 0.10% | C+ |
| American Airlinesthin sample | 296 | 81.2% | 106 min | 3.72% | B− |
| Frontier Airlinesthin sample | 238 | 67.5% | 93 min | 1.68% | C |
| Alaska Airlinesthin sample | 201 | 82.8% | 36 min | 1.49% | B |
| United Airlinesthin sample | 196 | 76.8% | 75 min | 0.51% | B+ |
| SkyWest Airlinesthin sample | 173 | 79.2% | 51 min | 0.00% | B+ |
| Delta Air Linesthin sample | 163 | 94.4% | 41 min | 1.23% | A |
| JetBlue Airwaysthin sample | 30 | 69.0% | 288 min | 3.33% | C− |
Route by route
Busiest routes out of ONT in June
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| ONT to DEN · Denverthin sample | 250 | 77.4% | 88 min | 0.00% | B+ |
| ONT to SEA · Seattlethin sample | 240 | 84.4% | 41 min | 1.25% | B |
| ONT to PHX · Phoenixthin sample | 224 | 78.3% | 80 min | 1.34% | B |
| ONT to DFW · Dallas-Fort Worththin sample | 210 | 75.9% | 84 min | 3.81% | B− |
| ONT to LAS · Las Vegasthin sample | 206 | 68.6% | 62 min | 0.97% | C+ |
| ONT to SMF · Sacramentothin sample | 177 | 76.8% | 44 min | 0.00% | B+ |
| ONT to SFO · San Franciscothin sample | 120 | 33.3% | 66 min | 0.00% | F+ |
| ONT to SJC · San Josethin sample | 114 | 75.4% | 62 min | 0.00% | B+ |
| ONT to SLC · Salt Lake Citythin sample | 113 | 96.5% | 30 min | 0.00% | A+ |
| ONT to OAK · Oaklandthin sample | 111 | 75.7% | 35 min | 0.00% | B+ |
| ONT to ATL · Atlantathin sample | 80 | 92.2% | 45 min | 2.50% | A |
| ONT to IAH · Houstonthin sample | 60 | 77.2% | 56 min | 5.00% | B− |
| ONT to HNL · Honoluluthin sample | 57 | 91.2% | 47 min | 0.00% | A+ |
| ONT to PDX · Portlandthin sample | 51 | 96.1% | 75 min | 0.00% | A+ |
| ONT to DAL · Dallasthin sample | 30 | 66.7% | 69 min | 0.00% | C+ |
| ONT to ORD · Chicagothin sample | 30 | 86.2% | 39 min | 0.00% | A+ |
| ONT to BNA · Nashvillethin sample | 30 | 67.9% | 29 min | 3.33% | C− |
| ONT to BWI · Baltimorethin sample | 30 | 100.0% | — | 0.00% | A+ |
| ONT to HOU · Houstonthin sample | 30 | 53.3% | 35 min | 0.00% | F+ |
| ONT to MDW · Chicagothin sample | 30 | 80.0% | 33 min | 0.00% | B+ |
| ONT to AUS · Austinthin sample | 30 | 70.0% | 44 min | 0.00% | C+ |
| ONT to CLT · Charlottethin sample | 30 | 80.0% | 47 min | 0.00% | B+ |
| ONT to JFK · New Yorkthin sample | 30 | 69.0% | 288 min | 3.33% | C− |
Delay causes
What held ONT up in June
Late-arriving aircraft accounts for 52% of the 35,000 delay minutes carriers reported here, and the remaining four split what is left.
- 52%Late-arriving aircraft
- 26%Carrier
- 21%National Airspace System
- 1%Extreme weather
- 0%Security
52% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 35,000 reported delay minutes here, that single category outweighs weather by 52 to one. The split is drawn from 34,777 reported delay minutes.
Cancellations sit at 1.00% against a national 1.65%, which is ordinary. Diversions add another 0.35%.
7.4% of arrivals land an hour or more late, close to the national 9.7%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
What to do with this
Flying from ONT in June
For a June trip through ONT: plan on this being one of the airport's harder months. The 5am–8am departures held up best at 94.4% on time, and with 7.4% of arrivals an hour or more late, a connection here deserves more slack than the same trip in February would.
Related
Where to go next
- Ontario International (ONT), the whole year
- ONT in September84.8%
- ONT in October81.6%
- ONT in November81.9%
- ONT in December82.4%
- ONT in January86.5%
- ONT in February87.8%
- ONT in March82.8%
- ONT in April82.8%
- ONT in May80.0%
- ONT in July77.9%
- ONT in August80.9%
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.