About 1 in 8 DL 3959 flights from Seattle arrived 15+ minutes late, diverted or cancelled over the past year (12%); 0.0% were cancelled. The typical flight landed 11 minutes early.
DL 3959: SEA → BOI
Scheduled to leave Seattle at 1:50 p.m. local time, operated by SkyWest as OO 3959. Over the past year it arrived on time 88% of the time (203 flights), worse than other DL flights on the route at that hour (92%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 30 | 90% |
| Tuesday | 29 | 90% |
| Wednesday | 29 | 90% |
| Thursday | 29 | 79% |
| Friday | 29 | 86% |
| Saturday | 29 | 97% |
| Sunday | 28 | 86% |
Why it was late
All flights SEA → BOI · Connecting off DL 3959? Check the risk
Questions
How often is DL 3959 from SEA to BOI late?
Delta Air Lines 3959 from Seattle, WA to Boise, ID arrived 15 or more minutes late, was diverted or was cancelled on 12% of 203 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check Delta Air Lines for today's flight. Method.