SEA to BOS flight delays
Seattle, WA (SEA) Boston, MA (BOS) · 2,496 miles
278 flights · March 2025 – August 2026 · US Bureau of Transportation Statistics
70.8%
Arrived on time
Within 15 minutes of schedule
0.72%
Cancelled
Share of scheduled flights
56 min
When late, late by
Average across delayed arrivals
17 min
Delay per flight
Averaged over every flight flown
What the record says about this route
This is a thin route — 278 flights across the whole period. On a route this infrequent a cancellation is far more costly than the rate suggests, because the next departure may not be the same day.
Flights from Seattle to Boston run late more often than the average route, though not severely.
The 2 airlines here are separated by under 3 points — close enough to call a tie. Choose on price and departure time.
Which airline should you fly on this route?
Over March 2025 – August 2026, Delta Air Lines arrived on time most often on SEA to BOS. Alaska Airlines was late most often.
Every airline on SEA to BOS
Ranked by how many flights each one operated. A carrier with fewer than 100 flights in the period is listed but not graded.
| Airline | Flights | On time | Cancelled | Avg delay | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 117 | 76.92% | 0% | 45 min | C |
| Delta Air Lines | 113 | 79.82% | 1.77% | 56 min | C |
| JetBlue Airways | 48 | 35.42% | 0% | 65 min | — |
The return leg
BOS to SEA Boston back to Seattle 74.55% on time COther routes from Seattle
Common questions
Are flights from Seattle to Boston usually delayed?
70.8% of flights on the SEA to BOS route arrived within 15 minutes of schedule, so roughly 3 in every ten arrived late. That is worse than the average route in this record.
Which airline is most on time from Seattle to Boston?
Delta Air Lines, at 79.82% on time across 113 flights. The least punctual on the route was Alaska Airlines at 76.92%.
How often are SEA to BOS flights cancelled?
0.72% of scheduled flights did not operate — about 7 in every thousand. That is in the normal range.
When SEA to BOS flights are late, how late are they?
About 56 minutes on average across the flights that arrived more than 15 minutes behind schedule.
What these figures do and do not tell you
Everything on this page is counted from the flights that actually operated on SEA to BOS during March 2025 – August 2026, as reported by the airlines to the US Bureau of Transportation Statistics. "On time" is the federal definition: arriving at the gate within 15 minutes of the scheduled time.
A route's record is a description of the past, not a forecast. Weather, air traffic control and the aircraft's earlier flights that day drive most delays, and none of them are predictable from a historical rate. What the record does tell you is whether this route runs late more often than others, and which carrier on it has the better history — which is the part you can actually act on when you book.
Cancellations are counted separately from delays because they are a different problem for a traveller: a late flight still gets you there. How the grade is calculated →