Seattle (SEA) to Boston (BOS): On-Time Performance
Data through May 2026
Seattle (SEA) to Boston (BOS) effectively runs on two schedules. In April 2025, 88% of arrivals were on time; in July 2025 that fell to 59% — a 29-point seasonal swing. Across the full period the route averages 76% on-time against a national 78%.
- On-time
- 76%
- arrived <15 min late
- Avg delay
- 16 min
- completed flights
- Cancelled
- 0.9%
- Flights/day
- 6.7
- last 12 months
- Duration
- 5h 25m
- scheduled
- Distance
- 2,496 mi
Best airline from SEA to BOS
3 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| Delta Air Linesmost reliable | 84% | 12 min | 1.2% | 1,908 |
| Alaska Airlines | 73% | 14 min | 0.7% | 2,375 |
| JetBlue Airways | 62% | 36 min | 1.0% | 696 |
Monthly on-time trend
Best time to fly from SEA to BOS
Aim for departures around 4 p.m. (97% on-time); avoid 10 a.m. departures (55%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 76% | 17 min |
| Tuesdaybest | 79% | 16 min |
| Wednesday | 78% | 14 min |
| Thursday | 72% | 19 min |
| Friday | 74% | 16 min |
| Saturday | 76% | 16 min |
| Sunday | 73% | 17 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft27%
- Airline operations36%
- National airspace system31%
- Weather6%
Frequently asked questions
- How often are flights from SEA to BOS delayed?
- 25% of SEA–BOS flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-06 and 2026-05. The average arrival delay across completed flights was 16 minutes.
- Which airline is most reliable from SEA to BOS?
- Delta Air Lines has the best on-time record on this route at 84%, based on 1,908 flights. 3 airlines flew SEA–BOS frequently enough to compare in this period.
- What is the best time of day to fly from SEA to BOS?
- Departures around 4 p.m. have the best record (97% on-time), while departures around 10 a.m. have the worst (55%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from SEA to BOS?
- The scheduled SEA–BOS flight time averages 5h 25m over 2,496 miles. Actual arrival times vary — flights on this route land 15+ minutes late 25% of the time.
- How often are SEA to BOS flights cancelled?
- 0.9% of scheduled flights on this route were cancelled between 2024-06 and 2026-05, at or below the national rate of 1.6%.
- What is the worst month to fly from SEA to BOS?
- July 2025 was the roughest month in this dataset, with only 59% of arrivals on time. The best was April 2025 at 88%. If your dates are flexible, that 29-point gap is worth planning around.
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Based on 4,979 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.