Seattle to Washington

What the Data Says About SEA to IAD

The Seattle to Washington corridor (SEA → IAD) covers roughly 2,306 miles and is served by 8 carriers, based on Bureau of Transportation Statistics reporting. Across 10,099 flights in the dataset, this route posts a 83.2% on-time rate with an average delay of 64.9 minutes when flights run late. Over the most recent 24 months of BTS data, 4,201 flights were recorded on this pairing — 51 cancelled (1.2%) and 17 diverted (0.4%). Those baseline metrics tell you what to expect before you book.

Having 8 carriers on the route matters: more carriers generally means more daily schedule options, competitive pricing, and redundancy when flights are cancelled. With 10,099 total flights analyzed, the 83.2% on-time figure is statistically meaningful rather than a small-sample fluke. The 64.9-minute average delay applies only to flights that actually ran late, so it is not the average wait across all departures — the majority of flights on this route depart on time under the BTS definition of a delay (15+ minutes past schedule).

Looking at recent months, Nov 2024 posted the best performance on this corridor at 89% on-time, while Jul 2025 came in at 70% on-time — a 19-point gap between best and worst recent month. For travelers evaluating the SEA to IAD route, the combination of a 83.2% on-time rate, 64.9-minute average delay, 1.2% recent cancellation rate, and 8 available carriers is the concrete summary of what BTS data shows about reliability on this pairing.