Islip, NY

What the Data Says About ISP

Islip, NY in Islip, New York handled 54,300 flights in the Bureau of Transportation Statistics dataset between 2020 and 2025, posting a 77.9% on-time departure rate. Of those flights, 11,984 experienced delays, 881 were cancelled, and 75 were diverted. The cancellation rate works out to 1.62%, the diversion rate to 0.14%, and the average delay when departures run late is 71.0 minutes. These figures are the baseline for comparing ISP against other airports in the same state and nationally.

Breaking down what drives delays at ISP, Late Aircraft leads the pack. Late Aircraft accounts for 45.0% of total delay minutes, followed by Carrier at 26.4% and NAS (National Aviation System) at 25.5%. Weather contributes 3.0% 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, November runs the cleanest at ISP with a 92% on-time rate, while July is the roughest at 85.3% — a 7-point swing between best and worst month. Volume peaks in March, when average flights hit 891. The busiest route from ISP is to MCO (Orlando), with 7,628 flights at a 77.6% on-time rate. Combine these numbers — 77.9% on-time, 71.0-minute average delay, 1.62% cancellation rate — and you have a concrete picture of departure reliability at Islip, NY.