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Route · SEA → BOS · 2020–2025 BTS data

Seattle to Boston

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), SEA to BOS (Seattle to Boston) ranks #723 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

77.2%
On-time
-1.8 pts
vs US avg
66 min
Delay when late
13,741
Flights
#723 of 4927
Corpus placement

Cancelled

0.8%

Best Month

Apr 2025 88%

Worst Month

Jul 2025 60%

Distance

2,496 mi

Carriers

9

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 161 22 2 0 DL,AS
Nov 2025 164 27 1 6 AS,DL
Oct 2025 227 62 2 0 AS,B6,DL
Sep 2025 229 75 0 0 DL,AS,B6
Aug 2025 270 94 0 2 AS,B6,DL
Jul 2025 274 109 4 1 AS,B6,DL
Jun 2025 255 75 2 0 AS,B6,DL
May 2025 228 85 2 0 AS,B6,DL
Apr 2025 196 23 1 0 AS,B6,DL
Mar 2025 191 31 1 1 AS,B6,DL
Feb 2025 146 25 5 0 AS,B6,DL
Jan 2025 150 25 1 0 AS,B6,DL
Dec 2024 185 51 0 1 AS,B6,DL
Nov 2024 187 24 0 0 B6,AS,DL
Oct 2024 230 36 0 0 AS,DL,B6
Sep 2024 234 59 0 0 AS,B6,DL
Aug 2024 273 97 2 0 AS,B6,DL
Jul 2024 271 71 5 0 AS,B6,DL
Jun 2024 252 57 1 1 AS,B6,DL
May 2024 238 63 2 1 AS,B6,DL
Apr 2024 210 65 0 0 AS,B6,DL
Mar 2024 189 37 0 0 AS,B6,DL
Feb 2024 154 33 0 0 AS,B6,DL
Jan 2024 157 43 10 0 AS,B6,DL

SEA–BOS seasonal on-time pattern

Best: March (83.7%) · weakest: June (71.9%)

70%75%80%85% JanFebMarAprMayJunJulAugSepOctNovDec 76.3%

Strongest calendar month

March

83.7% on-time · ~178 flights/mo

Busiest calendar month

August

~241 flights/mo avg

Weakest calendar month

June

71.9% on-time · ~208 flights/mo

Cancellation Rate

0.8%

41 of 5,071 flights

Diversion Rate

0.3%

13 of 5,071 flights

Explore origin & destination

On-time and delay data for the airports this route connects.

SEA - Seattle

Full on-time, delay-cause, and seasonal performance for Seattle, WA.

SEA on-time profile

BOS - Boston

Full on-time, delay-cause, and seasonal performance for Boston, MA.

BOS on-time profile

Compare the two airports

See SEA and BOS side by side on delays, cancellations, and reliability.

Compare SEA vs BOS

Origin-hub reliability standing

Mid-pack among SEA departures

From SEA, this corridor sits with 63 other 75–85% on-time routes out of 89 tracked departures, not the hub's reliability leaders (25 at ≥85%) and not the softest ( 1 below 75%). Destination: Boston · fleet on-time rank #4055 of 4927.

What the Data Says About SEA to BOS

The Seattle to Boston corridor (SEA to BOS) posts a 77.2% on-time rate on the lower edge of the average band, based on 13,741 tracked flights. Late flights run 66.4 minutes behind on average. 9 carriers cover the 2,496-mile route; over the last 24 months, 41 of 5,071 flights were cancelled (0.8%) and 0.3% diverted.

The monthly split is wide on this route: Apr 2025 posted the strongest performance at 88% on-time, while Jul 2025 came in at just 60% - a 28-point swing worth factoring into travel timing.

On the multi-year calendar, SEA–BOS peaks in March at 83.7% on-time while August carries the heaviest traffic (~241 flights per month) ; the softest month is June at 71.9%, a 11.8-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does SEA to BOS rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, SEA to BOS ranks #723 of 4927 tracked domestic routes by total flights (most flights = #1). That ordinal matches our busiest-routes listing (total_flights DESC). See /methodology#corpus-placement for the exact sort basis.
How often are flights delayed from SEA to BOS? ▼
Flights from Seattle to Boston have a 77.2% on-time rate based on 13,741 flights. The average delay is 66.4 minutes. The best recent month was Apr 2025 with 88% on-time.
What is the cancellation rate for SEA to BOS? ▼
Over the last 24 months, 0.8% of flights on this route were cancelled (41 of 5,071 flights) and 0.3% were diverted.
How far is the flight from SEA to BOS? ▼
The flight distance from Seattle (SEA) to Boston (BOS) is approximately 2,496 miles. This route is served by 9 carriers.
When is the best time to fly from SEA to BOS? ▼
The best recent month for on-time performance was Apr 2025 (88% on-time). The worst was Jul 2025 (60% on-time). Consider booking during months with historically better performance.

Airports on this route

SEA Airport

Seattle
BOS Airport

Boston
Data source

Data Source: Bureau of Transportation Statistics (BTS), On-Time Performance Data. Statistics reflect cumulative performance across all available reporting periods.

Read our methodology - how this data is sourced, computed, and verified.

Using SEA–BOS data

SEA–BOS is mid-pack at 77.2% on-time; month and carrier mix move more than the corridor headline.

  • Compare SEA and BOS airport profiles: delay causes and top routes differ even on the same corridor. SEA airport
  • If your dates flex, March (83.7% on-time) beats June (71.9%) on this corridor. Seasonal chart
  • 4 other routes post a similar 77.2% on-time rate; compare before you commit to this pairing. Similar routes

On-time rate reflects the BTS historical average across all reporting carriers on this origin–destination pair, not any single flight or booking recommendation.

Data sourced from U.S. Department of Transportation Bureau of Transportation Statistics (BTS) On-Time Performance data. See our methodology for details. Retrieved and formatted by PlainFlights

Every figure on PlainFlights is rendered directly from BTS On-Time Performance data, no number is typed in by an editor. This page aggregates this specific route's on-time performance and monthly trend, live from the dataset. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.