Route profile
BOS→SEA
Flight reliability, delays and best times to fly from Boston to Seattle, 2,496 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 50% of comparable major US routes (4,598 compared)
Calculated from 7,905 flights. How this is calculated
BOS → SEA arrives on time 75.7% of the time; the return trip, SEA → BOS, arrives on time 75.2% of the time.
BOS → SEA spends 37.3 minutes on the ground on a 2,496-mile trip: 24.4 minutes from pushback to wheels-up at BOS and 12.9 minutes from touchdown to gate at SEA.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What sets this route apart
Where BOS to SEA differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
BOS to SEA struggles most at 7 AM: 78.5% of its flights scheduled then arrive on time, 7 points behind the 85.5% on routes of similar length at the same hour. Against all other routes the gap is 9.3 points.
BOS to SEA is at its best against routes of similar length for flights scheduled at 11 AM: 83.8% arrive on time, 6.2 points ahead of the 77.6% those routes manage at that hour.
Thursday is the day BOS to SEA slips furthest against routes of similar length, 72.0% on time where they average 77.1%, 5.1 points lower. Against all other routes the gap is 4.8 points.
In June, BOS to SEA runs 10.5 points below routes of similar length, 63.8% on time to 74.3%. Against all other routes the gap is 8.9 points.
JetBlue’s flights on BOS to SEA arrive on time 71.8% of the time, 3.6 points below the 75.4% it manages on its routes of similar length.
BOS to SEA against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 7 AM departures | 78.5% | routes of similar length | 85.5% | −7.0 pts | 2,267 here, 99,229 there |
| Hour: 11 AM departures | 83.8% | routes of similar length | 77.6% | +6.2 pts | 741 here, 46,163 there |
| Weekday: Thursday | 72.0% | routes of similar length | 77.1% | −5.1 pts | 1,148 here, 144,081 there |
| Month: June | 63.8% | routes of similar length | 74.3% | −10.5 pts | 778 here, 87,365 there |
| Airline: JetBlue | 71.8% | routes of similar length | 75.4% | −3.6 pts | 1,197 here, 116,563 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 2,496 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
Why BOS → SEA flights are cancelled
July 2023 – July 2026
BOS → SEA cancelled 79 of 7,905 scheduled flights — about 1 in every 100. The reason filed most often was the airline, 69.6% of the cancellations coded on this route — about 1 in every 144 scheduled flights.
Share of cancellations
Of 79 cancelled departures carrying a reason code.
What each reason means
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
55 cancellations, 69.6% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
21 cancellations, 26.6% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
3 cancellations, 3.8% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
79 coded cancellations were recorded on BOS → SEA; the section appears from 50.
When it goes wrong
July 2023 – July 2026
42 min late
against a median of 6 min early
Percentiles over 7,905 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SEA after arriving from BOS.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 40% | Likely to miss |
| 45 min | 23% | High risk |
| 60 min | 14% | Some risk |
| 90 min | 6.9% | Some risk |
| 120 min | 4.2% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.00% of the time and diverts 0.29% of the time, which a late arrival never shows up in.
Chance of missing is the share of 7,803 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 42 minutes late (90th-percentile gate arrival delay), over 7,905 operations.
Any other layover length: connection checker.
Best time to fly
BOS → SEA flights departing 5–9 AM arrived on time 80.2% of the time, against 66.8% for 6–9 PM departures, a gap of 13.4 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 91.3% on time from 358 flights
- 7 AM: 78.5% on time from 2,298 flights
- 8 AM: too few flights to score
- 9 AM: 76.7% on time from 628 flights
- 10 AM: 70.6% on time from 232 flights
- 11 AM: 83.8% on time from 749 flights
- 12 PM to 2 PM: too few flights to score
- 3 PM: 79.8% on time from 214 flights
- 4 PM: 71.9% on time from 475 flights
- 5 PM: 77.8% on time from 765 flights
- 6 PM: 68.2% on time from 1,315 flights
- 7 PM: 64.8% on time from 808 flights
- 8 PM to 11 PM: too few flights to score
Why BOS → SEA runs late
July 2023 – July 2026
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for BOS → SEA. Only delays of 15 minutes or more are attributed.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Alaska Airlines | 3,717 | 73.9% | 1.02% | -5 min | 6.3% |
| Delta Air Lines | 2,980 | 79.4% | 1.07% | -8 min | 5.6% |
| JetBlue | 1,208 | 71.8% | 0.75% | -4 min | 12.8% |
Alaska Airlines flew 47.0% of the 7,905 flights listed.
Delta Air Lines arrived on time 7.6 percentage points more often than JetBlue on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
DL384 (7:25 AM) arrived on time 82.9% of the time, 19.0 points more often than B6197 (6:29 PM) at 63.9%.
Weekly and seasonal patterns
By day of week
Monday is historically the most reliable day and Thursday the least, a gap of 7.1 percentage points.
By month
- Jan: 78.7%
- Feb: 80.7%
- Mar: 71.8%
- Apr: 80.1%
- May: 80.3%
- Jun: 63.8%
- Jul: 68.5%
- Aug: 74.7%
- Sep: 84.5%
- Oct: 81.7%
- Nov: 80.9%
- Dec: 71.0%
June is historically the weakest month and September the strongest, a spread of 20.7 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 68.9% from 268 flights
- August 2023: 73.2% from 271 flights
- September 2023: 81.0% from 227 flights
- October 2023: 85.8% from 228 flights
- November 2023: 76.7% from 203 flights
- December 2023: 89.6% from 184 flights
- January 2024: 78.9% from 158 flights
- February 2024: 95.4% from 153 flights
- March 2024: 87.1% from 188 flights
- April 2024: 81.8% from 210 flights
- May 2024: 78.9% from 237 flights
- June 2024: 50.2% from 252 flights
- July 2024: 73.1% from 271 flights
- August 2024: 67.9% from 274 flights
- September 2024: 88.4% from 234 flights
- October 2024: 79.7% from 232 flights
- November 2024: 88.2% from 186 flights
- December 2024: 78.9% from 186 flights
- January 2025: 85.4% from 151 flights
- February 2025: 69.3% from 145 flights
- March 2025: 85.3% from 192 flights
- April 2025: 80.9% from 195 flights
- May 2025: 83.1% from 227 flights
- June 2025: 65.4% from 255 flights
- July 2025: 61.4% from 274 flights
- August 2025: 83.0% from 271 flights
- September 2025: 84.2% from 229 flights
- October 2025: 79.6% from 228 flights
- November 2025: 77.8% from 163 flights
- December 2025: 39.2% from 161 flights
- January 2026: 70.2% from 131 flights
- February 2026: 75.0% from 128 flights
- March 2026: 40.0% from 172 flights
- April 2026: 77.2% from 172 flights
- May 2026: 79.1% from 254 flights
- June 2026: 74.5% from 278 flights
- July 2026: 70.5% from 317 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 72.3% against 77.0% in the 12 months before — declining by 4.7 percentage points.
Data and methodology
Calculated by FlyerIntel from 7,905 BOS → SEA flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed