Air travel
How often are flights at Ontario (ONT) late?
In the 12 months through August 2026, 19.2% of flights leaving Ontario (ONT) left 15 or more minutes late, the 27th fewest of the 102 U.S. airports with at least 10,000 departures, against 22.9% of all U.S. flights. Airlines cancelled 0.9% of its scheduled departures (1.9% nationwide), the 12th fewest of the 102. Its worst month was June 2026, when 26.4% left late. Flights scheduled to leave in the 8 p.m. hour were late most often (37.2%), and those before 6 a.m. least often (5.5%).
Left 15+ minutes late
19.2%
The 27th fewest of 102 airports
Cancelled
0.9%
The 12th fewest of 102 airports
Worst month
June 2026
26.4% left late
Flights leaving Ontario (ONT) 15+ minutes late, each month
The interactive chart needs JavaScript. The numbers are in the tables below.
Flights leaving Ontario (ONT) 15+ minutes late, by scheduled departure hour
The interactive chart needs JavaScript. The numbers are in the tables below.
Hours are local time at Ontario. Delays build through the day as late planes make their next flights late too. Hours with fewer than about one flight a day are left out.
The numbers
Departures from Ontario (ONT) each month and each scheduled departure hour.
| Month | Scheduled | Left late | Cancelled |
|---|---|---|---|
| September 2025 | 2,177 | 15.2% | 0.5% |
| October 2025 | 2,265 | 19.0% | 0.5% |
| November 2025 | 2,184 | 17.5% | 2.1% |
| December 2025 | 2,132 | 20.6% | 0.7% |
| January 2026 | 1,892 | 16.3% | 1.7% |
| February 2026 | 1,734 | 15.2% | 0.3% |
| March 2026 | 2,081 | 15.5% | 1.0% |
| April 2026 | 2,119 | 19.0% | 0.3% |
| May 2026 | 2,298 | 20.8% | 0.7% |
| June 2026 | 2,304 | 26.4% | 1.0% |
| July 2026 | 2,377 | 22.5% | 0.9% |
| August 2026 | 2,228 | 19.8% | 0.8% |
| Departure hour | Scheduled | Left late | Cancelled |
|---|---|---|---|
| Before 6 a.m. | 1,588 | 5.5% | 0.6% |
| 6 a.m. | 3,770 | 6.1% | 0.7% |
| 7 a.m. | 1,582 | 7.7% | 1.1% |
| 8 a.m. | 1,443 | 11.4% | 0.8% |
| 9 a.m. | 1,274 | 12.5% | 0.8% |
| 10 a.m. | 1,607 | 18.2% | 0.8% |
| 11 a.m. | 1,345 | 18.8% | 1.0% |
| Noon | 1,739 | 23.7% | 1.2% |
| 1 p.m. | 1,967 | 25.6% | 0.6% |
| 2 p.m. | 1,064 | 33.1% | 1.5% |
| 3 p.m. | 1,148 | 30.3% | 1.0% |
| 4 p.m. | 1,385 | 27.4% | 0.9% |
| 5 p.m. | 1,262 | 23.6% | 0.9% |
| 6 p.m. | 1,215 | 32.8% | 0.6% |
| 7 p.m. | 847 | 30.0% | 0.5% |
| 8 p.m. | 662 | 37.2% | 0.5% |
| 9 p.m. | 517 | 33.9% | 0.2% |
| 10 p.m. | 785 | 17.2% | 1.4% |
| 11 p.m. | 591 | 22.5% | 2.9% |
Source and notes
U.S. Bureau of Transportation Statistics, Airline On-Time Performance (Reporting Carrier On-Time Performance, 1987–present) (Public domain (U.S. government work)). Data from September 2025 through August 2026.
These are domestic flights of the large U.S. airlines that report to the Bureau of Transportation Statistics, including the regional airlines that fly for them. A flight is late when it leaves its gate 15 or more minutes after its scheduled time, out of the flights that left; cancellations are out of the flights scheduled. BTS posts each month about two months after it ends, and this page moves on a month when it does.