Boston (BOS) to Seattle (SEA): On-Time Performance
Data through July 2026
When you fly BOS to SEA matters as much as anything else about the booking: the route swung from 88% on-time in September 2024 to just 38% in December 2025. Across the full period the route averages 74% on-time against a national 78%. Morning departures also hold up better than evening ones (79% vs 67%), which matters most in the rough months.
- On-time
- 74%
- arrived <15 min late
- Avg delay
- 15 min
- completed flights
- Cancelled
- 1.1%
- Flights/day
- 6.9
- last 12 months
- Duration
- 6h 23m
- scheduled
- Distance
- 2,496 mi
Best airline from BOS to SEA
3 airlines flew this route regularly between 2024-07 and 2026-07.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| Delta Air Linesmost reliable | 77% | 15 min | 1.4% | 2,054 |
| JetBlue Airways | 76% | 17 min | 0.9% | 758 |
| Alaska Airlines | 72% | 15 min | 1.0% | 2,514 |
Monthly on-time trend
Best time to fly from BOS to SEA
Aim for departures around 11 a.m. (83% on-time); avoid 6 p.m. departures (64%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 77% | 15 min |
| Tuesday | 76% | 15 min |
| Wednesdaybest | 78% | 13 min |
| Thursday | 71% | 17 min |
| Friday | 73% | 15 min |
| Saturday | 75% | 16 min |
| Sunday | 73% | 16 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft36%
- Airline operations29%
- National airspace system33%
- Weather3%
Frequently asked questions
- How often are flights from BOS to SEA delayed?
- 26% of BOS–SEA flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-07 and 2026-07. The average arrival delay across completed flights was 15 minutes.
- Which airline is most reliable from BOS to SEA?
- Delta Air Lines has the best on-time record on this route at 77%, based on 2,054 flights. 3 airlines flew BOS–SEA frequently enough to compare in this period.
- What is the best time of day to fly from BOS to SEA?
- Departures around 11 a.m. have the best record (83% on-time), while departures around 6 p.m. have the worst (64%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from BOS to SEA?
- The scheduled BOS–SEA flight time averages 6h 23m over 2,496 miles. Actual arrival times vary — flights on this route land 15+ minutes late 26% of the time.
- How often are BOS to SEA flights cancelled?
- 1.1% of scheduled flights on this route were cancelled between 2024-07 and 2026-07, at or below the national rate of 1.6%.
- What is the worst month to fly from BOS to SEA?
- December 2025 was the roughest month in this dataset, with only 38% of arrivals on time. The best was September 2024 at 88%. If your dates are flexible, that 50-point gap is worth planning around.
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Based on 5,326 flights, 2024-07–2026-07. Source: US DOT Bureau of Transportation Statistics. Updated 2026-09-28.