Ontario, CA

What the Data Says About ONT

Ontario, CA in Ontario, California handled 272,856 flights in the Bureau of Transportation Statistics dataset between 2020 and 2025, posting a 82.3% on-time departure rate. Of those flights, 48,267 experienced delays, 2,519 were cancelled, and 239 were diverted. The cancellation rate works out to 0.92%, the diversion rate to 0.09%, and the average delay when departures run late is 67.3 minutes. These figures are the baseline for comparing ONT against other airports in the same state and nationally.

Breaking down what drives delays at ONT, Late Aircraft leads the pack. Late Aircraft accounts for 43.6% of total delay minutes, followed by Carrier at 35.3% and NAS (National Aviation System) at 17.7%. Weather contributes 3.3% of delay minutes at this airport, while security holds the smallest share at 0.1%. Travelers often overestimate the weather share; the BTS categorization shows late-arriving aircraft and carrier operations as the larger contributors.

Seasonally, February runs the cleanest at ONT with a 93.4% on-time rate, while June is the roughest at 90% — a 3-point swing between best and worst month. Volume peaks in October, when average flights hit 4,108. The busiest route from ONT is to ONT (Ontario), with 16,938 flights at a 81.2% on-time rate. Combine these numbers — 82.3% on-time, 67.3-minute average delay, 0.92% cancellation rate — and you have a concrete picture of departure reliability at Ontario, CA.