PlainFlights

Route · BOS → SEA · 2020–2025 BTS data

Boston to Seattle

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), BOS to SEA (Boston to Seattle) ranks #722 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

81.2%
On-time
+2.2 pts
vs US avg
70 min
Delay when late
13,744
Flights
#722 of 4927
Corpus placement

Cancelled

0.9%

Best Month

Feb 2024 95%

Worst Month

Dec 2025 42%

Distance

2,496 mi

Carriers

9

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 161 93 3 5 DL,AS
Nov 2025 163 36 1 0 AS,DL
Oct 2025 228 46 2 0 AS,B6,DL
Sep 2025 229 36 0 1 DL,AS,B6
Aug 2025 271 46 0 0 AS,B6,DL
Jul 2025 274 103 6 1 AS,B6,DL
Jun 2025 255 88 1 0 AS,B6,DL
May 2025 227 38 2 0 AS,B6,DL
Apr 2025 195 37 0 1 AS,B6,DL
Mar 2025 192 28 1 0 AS,B6,DL
Feb 2025 145 42 6 2 AS,B6,DL
Jan 2025 151 22 0 0 AS,B6,DL
Dec 2024 186 39 0 1 AS,B6,DL
Nov 2024 186 22 0 0 B6,AS,DL
Oct 2024 232 47 0 0 AS,DL,B6
Sep 2024 234 27 2 0 AS,B6,DL
Aug 2024 274 87 3 0 AS,B6,DL
Jul 2024 271 71 7 0 AS,B6,DL
Jun 2024 252 124 3 0 AS,B6,DL
May 2024 237 50 0 0 AS,B6,DL
Apr 2024 210 38 1 0 AS,B6,DL
Mar 2024 188 24 1 1 AS,B6,DL
Feb 2024 153 7 1 0 AS,B6,DL
Jan 2024 158 32 5 1 AS,B6,DL

BOS–SEA seasonal on-time pattern

Best: May (86.2%) · weakest: December (72.8%)

70%75%80%85%90% JanFebMarAprMayJunJulAugSepOctNovDec 72.8%

Strongest calendar month

May

86.2% on-time · ~191 flights/mo

Busiest calendar month

August

~242 flights/mo avg

Weakest calendar month

December

72.8% on-time · ~168 flights/mo

Cancellation Rate

0.9%

45 of 5,072 flights

Diversion Rate

0.3%

13 of 5,072 flights

Explore origin & destination

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

BOS - Boston

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

BOS on-time profile

SEA - Seattle

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

SEA on-time profile

Compare the two airports

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

Compare BOS vs SEA

Origin-hub reliability standing

Mid-pack among BOS departures

From BOS, this corridor sits with 49 other 75–85% on-time routes out of 60 tracked departures, not the hub's reliability leaders (6 at ≥85%) and not the softest ( 5 below 75%). Destination: Seattle · fleet on-time rank #2640 of 4927.

What the Data Says About BOS to SEA

13,744 tracked flights put the BOS to SEA pairing (Boston to Seattle) at a 81.2% on-time rate, squarely in line with the wider network. Delays that do occur run 69.7 minutes on average. Across the 2,496-mile route and its 9 carriers, the trailing 24 months show 0.9% cancelled and 0.3% diverted (5,072 flights sampled).

The monthly split is wide on this route: Feb 2024 posted the strongest performance at 95% on-time, while Dec 2025 came in at just 42% - a 53-point swing worth factoring into travel timing.

On the multi-year calendar, BOS–SEA peaks in May at 86.2% on-time while August carries the heaviest traffic (~242 flights per month) ; the softest month is December at 72.8%, a 13.4-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does BOS to SEA rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, BOS to SEA ranks #722 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 BOS to SEA? ▼
Flights from Boston to Seattle have a 81.2% on-time rate based on 13,744 flights. The average delay is 69.7 minutes. The best recent month was Feb 2024 with 95% on-time.
What is the cancellation rate for BOS to SEA? ▼
Over the last 24 months, 0.9% of flights on this route were cancelled (45 of 5,072 flights) and 0.3% were diverted.
How far is the flight from BOS to SEA? ▼
The flight distance from Boston (BOS) to Seattle (SEA) is approximately 2,496 miles. This route is served by 9 carriers.
When is the best time to fly from BOS to SEA? ▼
The best recent month for on-time performance was Feb 2024 (95% on-time). The worst was Dec 2025 (42% on-time). Consider booking during months with historically better performance.

Airports on this route

BOS Airport

Boston
SEA Airport

Seattle
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 BOS–SEA data

BOS–SEA is mid-pack at 81.2% on-time; month and carrier mix move more than the corridor headline.

  • Compare BOS and SEA airport profiles: delay causes and top routes differ even on the same corridor. BOS airport
  • If your dates flex, May (86.2% on-time) beats December (72.8%) on this corridor. Seasonal chart
  • 4 other routes post a similar 81.2% 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.