Washington, DC

What the Data Says About IAD

Washington, DC in Washington, Virginia handled 618,145 flights in the Bureau of Transportation Statistics dataset between 2020 and 2025, posting a 84.1% on-time departure rate. Of those flights, 98,139 experienced delays, 6,473 were cancelled, and 677 were diverted. The cancellation rate works out to 1.05%, the diversion rate to 0.11%, and the average delay when departures run late is 81.3 minutes. These figures are the baseline for comparing IAD against other airports in the same state and nationally.

Breaking down what drives delays at IAD, Carrier leads the pack. Carrier accounts for 37.9% of total delay minutes, followed by Late Aircraft at 30.2% and NAS (National Aviation System) at 22.4%. Weather contributes 9.5% 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 IAD with a 94.3% on-time rate, while July is the roughest at 87.9% — a 6-point swing between best and worst month. Volume peaks in August, when average flights hit 9,390. The busiest route from IAD is to ATL (Atlanta), with 20,387 flights at a 84.2% on-time rate. Combine these numbers — 84.1% on-time, 81.3-minute average delay, 1.05% cancellation rate — and you have a concrete picture of departure reliability at Washington, DC.